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Diffstat (limited to 'doc/FAQ')
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1 files changed, 11 insertions, 6 deletions
@@ -948,15 +948,20 @@ SELECT * 4.24) How do I do an outer join? - PostgreSQL 7.1 and later supports outer joins. Here is an example: + PostgreSQL 7.1 and later supports outer joins. Here are two examples: + SELECT * + FROM t1 LEFT OUTER JOIN t2 ON (t1.col = t2.col); + + or SELECT * FROM t1 LEFT OUTER JOIN t2 USING (col); - This will join t1.col to t2.col, and return any unjoined rows in t1 - with NULL values for t2 columns. A RIGHT join would return unjoined - rows of table t2. A FULL join would return unjoined rows from t1 and - t2. The word OUTER is optional and is assumed in LEFT, RIGHT, and FULL - joins. Ordinary joins are called INNER joins. + These identical queries join t1.col to t2.col, and return any unjoined + rows in t1. A RIGHT join would return unjoined rows of table t2. A + FULL join would return unjoined rows from t1 and t2. The word OUTER is + optional and is assumed in LEFT, RIGHT, and FULL joins. Ordinary joins + are called INNER joins. + In previous releases, outer joins can be simulated using UNION and NOT IN. For example, when joining tab1 and tab2, the following query does an outer join of the two tables: |