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Dynamic queries refer to queries that are dynamically created by Drupal, rather than being supplied as an explicit query string. All insert, update, delete, and merge queries must be dynamic. Select queries can be either static or dynamic. Hence, "dynamic query" usually refers to a dynamic Select query.

The Select query builder supports using expressions in the field list. Example expressions include "double the age field," "count of all name fields," and a substring of the title field. Note that many expressions may use SQL functions, and not all SQL functions are standardized across all databases. Module developers must ensure that only expressions compatible with supported databases are used. (See List of functions and operators)

This cheat sheet provides an overview of commonly used methods, classes, and interfaces for content entities.

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/sites/default/files/drupal-content-entity-8.0.pdf

Any query can have a corresponding "count query". A count query returns the number of rows in the original query. To get a count query from an existing query (which is a select query object implementing the SelectInterface), use the countQuery() method.

This cheat sheet provides an overview of commonly used methods, classes, and interfaces for content entities.

Download

/sites/default/files/drupal-content-entity-8.0.pdf

This cheat sheet provides an overview of commonly used methods, classes, and interfaces for content entities.

Download

/sites/default/files/drupal-content-entity-8.0.pdf

Merge queries are a special type of hybrid query. Although the syntax for them is defined in the SQL 2003 specification, virtually no database supports the standard syntax. However, most provide an alternative implementation using database-specific syntax. Drupal’s merge query builder abstracts the concept of a merge query into a structured object that can be compiled into the appropriate syntax for each database. They are sometimes referred to as "UPSERT" queries, a combination of UPDATE and INSERT.

Select queries always return a result set object containing zero or more records. There are several ways to retrieve data from this result set depending on the use case. Records are fetched as objects by default unless you change the fetch mode (see: setFetchMode).

The most common use case is iterating over the result set with a foreach() loop.