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- #6681 - Support for WHEN NOT MATCHED BY SOURCE for MERGE statement [CORE6448]. - #6942 - Incorrect singleton error with MERGE and RETURNING.
97 lines
2.8 KiB
Plaintext
97 lines
2.8 KiB
Plaintext
-----------------
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MERGE statement
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-----------------
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Function:
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Read data from the source and INSERT, UPDATE or DELETE in the target table depending on a
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condition.
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Author:
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Adriano dos Santos Fernandes <adrianosf@gmail.com>
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Format:
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<merge statement> ::=
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MERGE
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INTO <table or view> [ [AS] <correlation name> ]
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USING <table or view or derived table> [ [AS] <correlation name> ]
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ON <condition>
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<merge when>...
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[<plan clause>]
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[<order by clause>]
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[<returning clause>]
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<merge when> ::=
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<merge when matched> |
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<merge when not matched by target> |
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<merge when not matched by source>
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<merge when matched> ::=
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WHEN MATCHED [ AND <condition> ] THEN
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{ UPDATE SET <assignment list> | DELETE }
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<merge when not matched by target> ::=
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WHEN NOT MATCHED [ BY TARGET ] [ AND <condition> ] THEN
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INSERT [ <left paren> <column list> <right paren> ]
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VALUES <left paren> <value list> <right paren>
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<merge when not matched by source> ::=
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WHEN NOT MATCHED BY SOURCE [ AND <condition> ] THEN
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{ UPDATE SET <assignment list> | DELETE }
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Syntax rules:
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1. At least one <merge when> clause should be specified.
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Scope:
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DSQL, PSQL
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Examples:
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1.
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MERGE
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INTO customers c
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USING (SELECT * FROM customers_delta WHERE id > 10) cd
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ON (c.id = cd.id)
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WHEN MATCHED THEN
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UPDATE SET
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name = cd.name
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WHEN NOT MATCHED THEN
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INSERT (id, name)
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VALUES (cd.id, cd.name)
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2.
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MERGE
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INTO customers c
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USING new_customers nc
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ON (c.id = nc.id)
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WHEN MATCHED THEN
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UPDATE SET
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name = cd.name
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WHEN NOT MATCHED BY SOURCE THEN
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DELETE
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Notes:
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A join is made between USING and INTO tables.
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The join type depends on the presence of
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<merge when not matched by source> and <merge when not matched by target>:
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- <merge when not matched by target> + <merge when not matched by source>: FULL JOIN
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- <merge when not matched by source>: RIGHT JOIN
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- <merge when not matched by target>: LEFT JOIN
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- only <merge when matched>: INNER JOIN
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As soon it's decided if the source and target has a matching, the set of the
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corresponding (WHEN MATCHED / WHEN NOT MATCHED) statements is evaluated in the order specified,
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to check their optional conditions. The first statement which has its condition evaluated to true
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is the one which will be executed, and the subsequent ones will be ignored.
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If no record is returned in the join, no action will be called.
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<merge when matched> is called when a match between source and target exists.
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UPDATE or DELETE will change the target table.
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<merge when not matched by target> is called when a source record matches no record in target.
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INSERT will change the target table.
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<merge when not matched by source> is called when a target record matches no record in source.
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UPDATE or DELETE will change the target table.
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That clause is allowed only since v5.
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