Sqlalchemy unique together. Here's the mapping class definition: About this document.

This URI specifies the database type and connection details. execute(query): Executes the query on the database. Mar 16, 2023 · Sqlalchemy unique will define the number of types abstracted from normal SQL types supported by the backend database. The usage of the Session should fit within a structure similar to this: try: # <use session> session. Lets assume I have a table like this. query(Hit. This ensures that the combination of values in these columns remains unique, preventing duplicate entries and maintaining data integrity. In this section, we will cover one more essential ORM concept, which is how the ORM interacts with mapped classes that refer to other objects. id INTEGER NOT NULL, name VARCHAR(255), email VARCHAR(255), login VARCHAR(255), Apr 7, 2017 · u_idx = UniqueConstraint(attr_2, attr_3, 'my_table_uidx') when I call create_database I will get sqlalchemy to create the table 'my_table' with all columns as specified. Jun 15, 2013 · "The biggest visible change in SQLAlchemy 2. name) FROM Skills AS filterS INNER JOIN UserSkills AS ufs ON filterS. In the expression session. Sep 21, 2013 · 10. You may also have a look at the following articles to learn more – I have the following SQLAlchemy class. Or use something similar to UniqueConstraint("id", "candidate_id") in the __table_args__. Remove all mappers from all classes. I tried unique_together but it doesn't seem working. merge() examines the primary key attributes of the source instance, and attempts to reconcile it with an instance of the same primary key in the session. soundimage. user_id INNER JOIN Skills AS userS ON us. Python sqlalchemy多列唯一约束 在本文中，我们将介绍如何使用Python的SQLAlchemy库来实现跨多个列的唯一约束。 阅读更多：Python 教程 什么是唯一约束？ 唯一约束是一种数据库约束，用于确保表中的某个或多个列的值是唯一的。这意味着不允许在这些列中插入重复的值。 Oct 8, 2008 · Use Uuid if your database does not support uuid types. Asking about how to model the database I was advised to use the following table structure for my many-to-many relationship: Apr 27, 2016 · I'm attempting to create using sqlalchemy a multi column unique constraint that will be picked up by Alembic in it's automatic upgrade script generator. Nov 14, 2022 · EDIT: session. In this case I can't really tell what you're going for. It’s important to note that the ForeignKeyConstraint is the only way to define a composite foreign key. Define a UniqueConstraint object, specifying the columns that should be unique together. class Jun 18, 2024 · Taken together, the combination of a string table name as well as a list of column declarations is known in SQLAlchemy as table metadata. You could foreign key to name, and THEN do a unique constraint on name and prop. And that matches with the sql code Jun 18, 2024 · Above, mapped_column() constructs are placed inline within the class definition as class level attributes. orm. bind ¶. This is the default behavior in SQLite, but not in MS SQL Server. 0 is the use of Session. Jun 18, 2024 · The sqlalchemy. This behavior can be configured at mapper construction time using the Nov 17, 2014 · All groups and messages May 14, 2018 · Download ZIP. But I don't want to have some duplicated rows for some columns. As of SQLAlchemy 1. Jun 18, 2024 · Release: | Release Date: June 18, 2024. You also can derive from your own model subclasses and you can make abstract models like this. Looks like sqlalchemy distinct () accepts only one column or expression. name)) This example creates a functional index on the length of the ‘name’ field. In SQLAlchemy, a popular Python library for working with databases, implementing unique constraints across multiple columns is straightforward Jan 28, 2021 · zzzeek. Example: from sqlmodel import Field, SQLModel, UniqueConstraint, create_engine. 4, there are two distinct styles of Core use known as 1. @PiotrKamoda If you need a composite primary key, just set primary_key=True to all the primary key fields. Import the database object and the student model, and then run the db. Jan 13, 2012 · This is the first time I've used ORM, so I'm not sure the best way to handle this. The following example defines a composite unique constraint for the Employee schema over the address and division property: The Jun 18, 2024 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. in the case of a single-column, i. skill_id INNER JOIN Users AS u ON ufs. See the section Autoflush for further background on this option. schema. I then tried using a Index (unique=True) instead. 0 style, the latter of which makes some adjustments mostly in the area of how transactions are controlled as well as narrows down the patterns for how SQL statement constructs are executed. The sqlalchemy docs have a writeup on the performance of various techniques that can be used for bulk inserts: ORMs are basically not intended for high-performance bulk inserts - this is the whole reason SQLAlchemy offers the Core in addition to the ORM as a first-class component. May 31, 2024 · SQLAlchemy では、 UniqueConstraint クラスを使用して、複数の列の値を組み合わせたユニーク制約を設定できます。. これは、同じ値の組み合わせがデータベースに複数回保存されるのを防ぐために役立ちます。. More specific scenarios you can get using subquery(). config ['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///example. Examples include counting, computing averages, as well as locating the maximum or minimum value in a set of values. May 10, 2023 · sqlalchemy. Model): b = db. Table A ----- id address now I want to get all rows of this table but for rows with the same adress I want to get only one row (doesn't matter which id). My question is how do I do that in SQLAlchemy and have it still work with SQLite. class User (Base): uuidtype1 = mapped_column (UUID, primary_key=True) uuidtype2 = mapped_column (Uuid) # Works with db with non native uuid. Applications should ensure some system of “framing” is applied to ORM Alright you should learn how to create minimal working examples. Its two primary arguments are the table name, then the MetaData object which it will be associated with. Ensuring the uniqueness of columns within a database table is crucial for maintaining data integrity, and SQLAlchemy provides intuitive syntax for defining unique constrain It’s important to note that the ForeignKeyConstraint is the only way to define a composite foreign key. My first table looks like this: class Address(db. SQLAlchemy, a widely used ORM for Python, provides an elegant way to select distinct rows from a database. 7 V Sep 8, 2022 · The SQLModel metaclass inherits a great deal from the SQLAlchemy DeclarativeMeta class. A big part of SQLAlchemy is providing a wide range of control over how related objects get loaded when querying. The simpler version, if you can live with duplicate values in your comma separated list: fromsqlalchemyimport*metadata=MetaData() MetaData is a container object that keeps together many different features of a database (or multiple databases) being described. # Configure the database. 2 V when it's nominal voltage is 3. Given a class, return the primary Mapper associated with the key. from sqlalchemy. Column(db. query(). In this example, SQLite is used as the database. id) has a subscription on. Learn more about bidirectional Unicode characters. invoice_id and invoice_item. Many things can cause a failure within the try/except besides flushes. distinct(Tag. Mar 4, 2024 · The SQLAlchemy ORM, in order to map to a particular table, needs there to be at least one column denoted as a primary key column; multiple-column, i. Defines a single column or composite UNIQUE constraint. The foreign key is also setup fine, but no unique index can be found on the database side. In “classical” form, the table metadata is created separately with the Table construct, then associated with the User class via the registry. e the elements in db need to be unique together with each other. Class decorator which will adapt a given class into a declarative_base (). close() # optional, depends on use case. The first parameter is the table name as defined in the database, and the second is Base. The default behavior of relationship () is to fully load the contents of collections into memory, based on a configured loader strategy that controls when and how these contents are loaded from the database. Home | Download this Documentation. commit() except: session. To review, open the file in an editor that reveals hidden Unicode characters. I'm using SQLAlchemy for my Flask application, and I wish to connect two tables, where the relationship should be made on two ForeignKey that are only unique together. Beyond using the ORM’s declarative system, you can also work directly with SQLAlchemy Core to create indexes. Basic Relationship Patterns ¶. At the point at which the class is declared, the Declarative mapping process will generate a new Table object against the MetaData collection associated with the Declarative Base; each instance of mapped_column() will then be used to generate a Column object during this process, which ADD CONSTRAINT uq_yourtablename UNIQUE(column1, column2); or. This tutorial covers the well known SQLAlchemy Core API that has been in use for many years. Jun 18, 2024 · Home Download this Documentation. composite, primary keys are of course entirely feasible as well. something like ix__uuid Below my code for table creation ad Relationship Loading Techniques ¶. Related collections may be loaded into memory not just when they are 在本文中，我们将介绍在使用 Flask 、SQLAlchemy 和 Python 的开发项目中，如何处理唯一数据的问题。. 2024-04-072021-09-17by Johnny Graber. query(Tag). name and produces the query (distinct on all fields): SELECT DISTINCT tag May 7, 2021 · In the Todo model below there is a unique constraint put on text column. By “related objects” we refer to collections or scalar associations configured on a mapper using relationship () . 唯一数据是指在数据库中不能存在重复值的数据。. OpenAlchemy documentation for composite unique constraints. classAbstractTournament(Model):id=fields. Here we discuss the introduction, unique database, and how to model SQLAlchemy unique with tables. In your case this would be: from sqlalchemy import Column, Integer, UniqueConstraint. declarative import declarative_base. I have create the constraint using: from sqlalchemy import UniqueConstraint in my model Nov 17, 2021 · I haven't tested it with SQL-Server but I reckon that you could use the string_agg function. idx = db. SQLAlchemy is a powerful Object-Relational Mapping (ORM) tool for Python, which allows developers to interact with databases using Python classes and objects. By “related objects” we refer to collections or scalar associations configured on a mapper using relationship() . Maintainer. I have a situation where I require things to be unique together i. A quick walkthrough of the basic relational patterns, which in this section are illustrated using Declarative style mappings based on the use of the Mapped annotation type. x style and 2. al/25cXVn--Music by Eric Matyashttps://www. DatetimeField(auto_now_add=True)classMeta:abstract=Truedef__str__(self):returnself. In order to get the unique constraints, issue a get_unique_constraints. order_by(asc(Order. If you create an SA model against an existing table that does not actually have this constraint present, it will be as if it does not exist. metadata , which provides the connection between the SQLAlchemy functionality and the database engine. Feb 1, 2018 · I am trying to port the following query to SQLAlchemy: SELECT u. yourtablename(column1, column2); Of course, it can often be better to check for this violation first, before just letting SQL Server try to insert the row and returning an exception (exceptions are expensive). CREATE UNIQUE INDEX uq_yourtablename. ¶. username, GROUP_CONCAT(DISTINCT userS. exc. note: for a newer pattern that's more targeted towards the goal of a "lookup" object attached to a parent, without needing to pass Session objects or use thread local sessions, see the Jan 3, 2024 · SQLAlchemy Composite Indexes: The Complete Guide ; Full-Text Search in SQLAlchemy: The Ultimate Guide ; SQLAlchemy: What if you don’t close database connections? SQLAlchemy: How to Remove FOREIGN KEY Constraints (2 Ways) SQLAlchemy: How to Create and Use Temporary Tables ; SQLAlchemy: Saving Categories and Subcategories in the Same Table . Nov 16, 2023 · In your Flask application, configure the database by setting the SQLALCHEMY_DATABASE_URI. email nullable (column constraint) True — is the default value (except for a primary key column) Jul 18, 2014 · 11. Query. For database that supports uuid, such as postgres, Uuid acts as UUID by default. For example: Relationship Loading Techniques. From the docs: New in version 2. Click OK in each window and you're done. db'. name. So, passing column expressions to distinct() works for PostgreSQL only (because there is DISTINCT ON ). In this post, I explore some more ways to use the same tools to validate the more complex case of validating a… About this document. This behavior can be configured at mapper construction time using the Mar 9, 2022 · This special shell runs commands in the context of your Flask application, so that the Flask-SQLAlchemy functions you’ll call are connected to your application. This is what the documentation says: Session. Sep 17, 2021 · Python Friday #89: Constraints, Indexes and Default Values in SQLAlchemy ORM. 0: The relationship() construct can derive the effective value of the relationship. Base = declarative_base() class Item(Base): __tablename__ = 'items'. to_sql to insert data into database table. According to the sqlalchemy documentation of defining constraints and indexes. Additionally, there are differences between the major RDBMS how those are defined (especially across multiple columns) and what is exactly possible. declarative system which automatically generates mapped classes and relationships from a database schema, typically though not necessarily one which is reflected. from sqlalchemy import UUID, Uuid. Recommended Articles. rollback() raise finally: session. Jun 21, 2013 · You probably want to produce a subquery and select from that, which you can achieve using query. Documentation for defining composite unique constraint in SQLAlchemy. unique_together may be deprecated in the future. execute(query) distinct_values = [row[ 'column_name'] for row in result] # Assuming 'column_name' column exists. class User(SQLModel, table=True): id: int = Field(primary_key=True) Jun 18, 2024 · Class Mapping API ¶. A two-tiered relationship which links two tables together using an association table in the middle. 1. " Reproducible example using pandas to collect the unique values. Oct 8, 2016 · I want the pheno categories to be unique, but I want to have a full association between the two tables. String(12)) c = db. sql. e. username should be unique, need to fix that, and I'm not sure why SQLalchemy creates some row names with the double-quotes. length(User. IntField(primary_key=True)name=fields. How can I narrow this constraint to validate uniqueness per &quot;foreign-keyed&quot; user only, not per all users as it is Jun 18, 2024 · MetaData is a container object that keeps together many different features of a database (or multiple databases) being described. I'm using the MySQL backend. The association relationship differs from a many to many relationship in that the many-to-many table is mapped by a full class, rather than invisibly handled by the sqlalchemy. connection. In this tutorial, we’ll cover how to use SQLAlchemy to write queries that return unique records. position)). user_id = u. Unique Object. This should be more efficient than using concat of two columns - with group by database would be able to use indexes if they do exist: session. Check the columns you want included. Integer, primary_key=True) Jul 10, 2023 · I am using df. If you have had a unique city column previously, and you haven't changed it from the Database, it will keep reinforcing the unique constraint on the column. Let us look how SQLAlchemy can help us with both. merge(company) works fine for me as I only need to check for primary key and not other unique values. This tutorial covers the well known SQLAlchemy ORM API that has been in use for many years. In the section Declaring Mapped Classes, the mapped class examples made use of a construct called relationship(). The SQLAlchemy pysqlite driver supports this mode of use by specifying “uri=true” in the URL query string. app. TextField()created=fields. For a no-frills, single column constraint, adding unique=True to the Column definition is a shorthand equivalent for an unnamed, single column UniqueConstraint. 📌. Is there any simple query to achieve this using SQLAlchemy session? Feb 13, 2022 · A table-level UNIQUE constraint. These columns do not need to be actually known to the database as primary key columns, though it’s a good idea that they are. UniqueConstraint provides more functionality than unique_together. Oct 20, 2014 · When present, the Postgresql dialect will render a DISTINCT ON (>) construct. user_agent). There isn't any way to convince MySQL to use a non-primary key for the clustered index. It is hoped that the AutomapBase system provides a quick and modernized solution to the problem that the very famous SQLSoup Jul 11, 2022 · Saved searches Use saved searches to filter your results more quickly I am trying to get a SQL Alchemy query of distinct items below filtering on related objects, the equivalent of the below query: SELECT distinct items. I would like to ensure that the invitations are unique across three columns: to_user, fro Jun 18, 2024 · In SQL, aggregate functions allow column expressions across multiple rows to be aggregated together to produce a single result. table created with: CREATE TABLE user (. The existing table is defined with the composite primary key. Lets say we have a model Things ( Rough PseudoCode) thing1_id = Column(Integer) thing2_id = Column(Integer) Now I need thing1_id and thing2_id to be a unique together ie Jun 18, 2024 · A SELECT statement constructed against a class in a joined inheritance hierarchy will query against the table to which the class is mapped, as well as any super-tables present, using JOIN to link them together. Flask SQLAlchemy multiple column unique constraint. ON dbo. autoflush () method is equivalent to using the autoflush execution option at the ORM level. This construct defines a linkage between two Jan 16, 2013 · I am writing a Flask/SQLAlchemy application in which I have users and groups. but it's not SQLAlchemy's job to second-guess explicit intent. Normally, a single instance of registry shared for all Nov 2, 2023 · Conclusion. uselist parameter from a given Mapped annotation. How do I create an class that is unique over 2 columns, and refer to that unique combination? Say each User is unique by his combination of name and email: Jun 18, 2024 · Automap. id WHERE 2. Jun 23, 2012 · 5. Say you have entities A and B, do this: from sqlalchemy. This is a guide to SQLAlchemy unique. 以下の例では、 users テーブルに username と email 列の Apr 5, 2017 · The definition of unique constraints in sqlalchemy is indeed only used in for schema generation (creating tables). If you don't care about using SQLAlchemy to manage your database schema (although, you probably should), you can simply set the UUID as the primary key in the SQLAlchemy schema and leave the add_id as the pk in the actual table. item_name FROM items INNER JOIN Sep 1, 2018 · In sql databases index are used speed up query performance. This question essentially two parts. I need to generate SQLALchemy query, that selects all texts from table A that do not have corresponding common value in table B, or for that row url == None. IntegrityError) UNIQUE constraint failed: authors. models. This models won’t be created in schema generation and Nov 23, 2015 · You could use SQLalchemy reflection API. Oct 2, 2013 · I'm trying to use SQLAlchemy with MySQL to create a table mapping for a table with a composite primary key, and I'm unsure if I'm doing it right. attributesqlalchemy. In many respects, you can treat an SQLModel subclass the way you would treat your SQLAlchemy ORM base class. Here's the mapping class definition: About this document. name). Because for the database, it still has a unique constraint. You can even specify your more complex primary keys in table args. Jun 18, 2024 · Working with ORM Related Objects. The SQLite-level “URI” is kept as the “database” portion of the SQLAlchemy url (that is, following a slash): Jan 3, 2024 · Removing duplicates from query results is a common necessity in data manipulation and analysis. Inherited from ColumnCollectionConstraint : Inherited from ColumnCollectionMixin (via The Python sqlite3 driver supports this mode under modern Python 3 versions. Jul 2, 2020 · SQLAlchemy as a library can be easily used for managing tables, even creating them, but only for once. orgTrack title: Over a M Jan 3, 2024 · Introduction. Jun 18, 2024 · The Database Toolkit for Python. item_id, items. id = us. To represent a table, use the Table class. Feb 24, 2020 · Primary key that is unique over 2 columns in SQLAlchemy Hot Network Questions Why battery uses 4. Indexing with SQLAlchemy Core. This is - when supported by sqlalchemy - handled by the dialect and more or less It’s important to note that the ForeignKeyConstraint is the only way to define a composite foreign key. Define an extension to the sqlalchemy. 4, there are two distinct styles of ORM use known as 1. Working with Large Collections ¶. Provide a column-level property for use with a mapping. I have a one-to-many relationship where each Parent can have many Children: class Parent(Base): __tablename__ Dec 13, 2020 · Using SQLAlchemy I'm a bit confused about composite keys (?), uniqueconstraint, primarykeyconstraint, etc. skill_id = userS. Mar 27, 2010 · NOTE: I know user. non-composite primary key, it is indeed redundant. – jadkik94. sessionId together with user. sql import func Index('ix_name_length', func. You would notice the use of the index key because the sql code generated is: UNIQUE KEY `ix_tt_t3` (`t3`) The way how sqlalchemy nouns the index is idx_%columnlabbel. Setting up table metadata using both Core and ORM approaches is introduced in the SQLAlchemy Unified Tutorial at Working with Database Metadata . The setup for each of the following sections is as follows: Other answers using uselist=False are correct, but in SQLAlchemy 2. map_imperatively () method, after establishing a registry instance. SQLAlchemy, when integrated with Flask, provides a robust framework for defining database models and Return a Query with a specific ‘autoflush’ setting. Check the Unique checkbox and click Add button. Raw. Aug 13, 2010 · Under the table, right click Indexes ->Click/hover New Index ->Click Non-Clustered Index A default Index name will be given but you may want to change it. If a customer has more than one Order with the requested vehicle id and date, you'll get two rows association relationship¶. Effective database management is crucial when building full-stack web applications. Add a new mapped attribute to an ORM mapped class. Jan 24, 2018 · There are no foreign keys between these two tables and I need to make common is common attribute of both tables. From the Django documentation for unique_together: Use UniqueConstraint with the constraints option instead. . create_all() function to create the tables that are associated with your models. ip_address, Hit. from sqlalchemy import create_engine. It seems the way to accomplish this in SQL Server is to use an index with a where clause, as described in this post. ref_num columns, SQLAlchemy would not be aware that these two values should be paired together - it would be two individual foreign key constraints instead of a single Jun 18, 2024 · Prerequisite Sections - the ORM focused part of the tutorial builds upon two previous ORM-centric sections in this document: Executing with an ORM Session - introduces how to make an ORM Session object. 处理唯一数据的方法对于构建健壮的应用程序非常重要，可以确保数据的一致性和完整性。. class MyClassA(db. Primary keys are unique, so you must issue a get_pk_constraint too. May 23, 2023 · In my previous post, I wrote about basic validations using constraints and validators. Users can belong to several groups, and they have a unique number within each group. relationship() construct as in the case with many-to-many, so that additional attributes I am new to sql alchemy and I would like to count unique rows in my table and output the unique rows together with the number of copies for that row. home; features Philosophy Statement; Feature Overview; Testimonials Jun 18, 2024 · It’s important to note that the ForeignKeyConstraint is the only way to define a composite foreign key. Another way around is to use group_by and count. \. Here are two common approaches to achieve uniqueness across multiple columns in SQLAlchemy: UniqueConstraint Class: Import the UniqueConstraint class from sqlalchemy. SQLAlchemy provides for SQL functions in an open-ended way using a namespace known as func. Sep 19, 2011 · If single table inheritance is not an option, you probably want to either (1) enforce uniqueness in python, or (2) abandon sqlalchemy inheritance, and just use a foreign key to link Foo and Bar to Parametric. ref_num columns, SQLAlchemy would not be aware that these two values should be paired together - it would be two individual foreign key constraints instead of a single Im building a table with index=True where i would like the name to always be a unique index name possible using UUID as suffix . How can I change this declaration to enforce that constraint? Jan 3, 2024 · from sqlalchemy. The following EventInvitation model is a simple invitation for one event, sent from a user to another user. 0 relationship is now smart enough to deduce it if your Mapped annotation uses a non-collection type. The query would then return objects that are of that requested type as well as any sub-types of the requested type, using the 上述代码中，我们首先使用SQLAlchemy创建了一个数据库引擎，并定义了一个MyModel模型，模型中的unique_field字段使用了unique=True参数来实现唯一性约束。 然后，我们使用 SessionLocal 来创建一个数据库会话，在会话中插入一条数据。 Nov 13, 2022 · Become part of the top 3% of the developers by applying to Toptal https://topt. mapper () standalone function is effectively removed. Model): __tablename__ = 'Address'. ext. String(12)) I want to make sure that the values of b are unique over the whole column. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. So instead of. I am sure this is simple, but I am struggling with a good way to do it, other than tracking all of the Pheno objects in a dictionary and linking them manually that way. connect() as connection: result = connection. 我们将学习如何在 Jun 15, 2024 · Creating Unique Constraints on Multiple Columns. or some such. expression import label. it is absolutely valid for a unique constraint to be placed on a column that is also part of a primary key constraint. count() sqlalchemy ignores Tag. The right index can boost the performance of your SQL query enormously while constrains help you to enforce the integrity of your data in the database. id = ufs. Using ORM Declarative Forms to Define Table Metadata - where we set up our ORM mappings of the User and Address entities. It's certainly possible to union different tables with sqlalchemy, you just have to specify what columns you're fetching out of each table so they can be combined properly. . py. 4, the Query. Loop through the result set and extract the distinct values. And I'm trying to come up with a way to retrieve all of the channels, as well as an indication on what channels one particular user (identified by user. Apr 28, 2024 · Execute the Query and Fetch Results: with engine. id INNER JOIN UserSkills AS us ON u. Apr 20, 2016 · I want to enforce a unique constraint on a column but only if it is not null. answered Sep 19, 2011 at 19:51. ref_num columns, SQLAlchemy would not be aware that these two values should be paired together - it would be two individual foreign key constraints instead of a single Using the constraints features UniqueConstraint is preferred over unique_together. ref_num columns, SQLAlchemy would not be aware that these two values should be paired together - it would be two individual foreign key constraints instead of a single The SQLAlchemy Table class creates a unique instance of an ORM mapped table within the database. from_self(). Mar 30, 2022 · When working with databases, it is often necessary to enforce unique constraints across multiple columns. Define and insert the iris dataset Composite unique constraints are unique constraints that span multiple columns. Those "unique=True" declarations are only used to impose database level table constraints, and only then if you create the table using a sqlalchemy command, i. execute() in conjunction with select() to run ORM queries, instead of using Session. While we could also have placed individual ForeignKey objects on both the invoice_item. on Jan 29, 2021. IntegrityError: (sqlite3. Various patterns for instantiating an object that may or may not correspond to an existing row, kept unique on some field or set of fields. 0 style, the latter of which makes a wide range of changes most prominently around how ORM queries are constructed and executed. bg of pl bq ao dt lx ks th oy