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authorBruce Momjian <bruce@momjian.us>2001-01-22 06:27:41 +0000
committerBruce Momjian <bruce@momjian.us>2001-01-22 06:27:41 +0000
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downloadpostgresql-505cdd5873aa101a58a80ee4bceb8000eb7f5a35.tar.gz
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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: