MergeQuery
class MergeQuery
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.
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