![]() If the data types of the parameters don't match, this will produce an error: postgres=# SELECT coalesce(1,now(),null) ĮRROR: COALESCE types integer and timestamp with time zone cannot be matched There are multiple NULLs in this expression, but because the first non-NULL value was reached on the third parameter, all remaining values were disregarded.Ĥ. Here is how it interprets multiple NULL values: postgres=# SELECT coalesce(null,null, 1, 2, 3, null, 4) The COALESCE function found a NULL value in the first parameter, so it continued to the second parameter, which was not NULL, so that parameter's value was returned.ģ. Here is how COALESCE works when a NULL value is the first parameter: postgres=# select coalesce (null,1,2) The COALESCE function finds the first non-NULL expression at the start, so it will always produce the same result regardless of what the remaining parameters contain.Ģ. Here is how COALESCE works with a non-NULL value for the first parameter: postgres=# select coalesce (1,null,2)
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