Merge

General class for an abstracted MERGE query operation.

An ANSI SQL:2003 compatible database would run the following query:

MERGE INTO table_name_1 USING table_name_2 ON (condition)
  WHEN MATCHED THEN
  UPDATE SET column1 = value1 [, column2 = value2 ...]
  WHEN NOT MATCHED THEN
  INSERT (column1 [, column2 ...]) VALUES (value1 [, value2 ...

Other databases (most notably MySQL, PostgreSQL and SQLite) will emulate this statement by running a SELECT and then INSERT or UPDATE.

By default, the two table names are identical and they are passed into the the constructor. table_name_2 can be specified by the MergeQuery::conditionTable() method. It can be either a string or a subquery.

The condition is built exactly like SelectQuery or UpdateQuery conditions, the UPDATE query part is built similarly like an UpdateQuery and finally the INSERT query part is built similarly like an InsertQuery. However, both UpdateQuery and InsertQuery has a fields method so MergeQuery::updateFields() and MergeQuery::insertFields() needs to be called instead. MergeQuery::fields() can also be called which calls both of these methods as the common case is to use the same column-value pairs for both INSERT and UPDATE. However, this is not mandatory. Another convenient wrapper is MergeQuery::key() which adds the same column-value pairs to the condition and the INSERT query part.

Several methods (key(), fields(), insertFields()) can be called to set a key-value pair for the INSERT query part. Subsequent calls for the same fields override the earlier ones. The same is true for UPDATE and key(), fields() and updateFields().

Hierarchy

• class \Drupal\Core\Database\Query\Query implements PlaceholderInterface
  • class \Drupal\Core\Database\Query\Merge implements ConditionInterface uses QueryConditionTrait

File

core/lib/Drupal/Core/Database/Query/Merge.php, line 46

Namespace

Drupal\Core\Database\Query

Members