Note: CASE or COALESCE catching NULL values are typically good style, but that's not what this question is about. It's a bit of a trick question as I know the answer. Test-#, (text 'foo' || col) IS NULL AS result_is_nullĪ client of mine stumbled over this, relying on the result to be NULL, and I found it intriguing enough to share. In other words, how is this possible? test=# SELECT col IS NULL AS col_is_null Is it possible to concatenate a text and a NULL value and get a non-null result?
The comparison operators compare the array contents element-by-element, using the default B-tree comparison function for the element data type, and. In addition to those, the usual comparison operators shown in Table 9.1 are available for arrays. Test-#, (NULL::bigint || text 'baz') IS NULL Table 9.52 shows the specialized operators available for array types.
Test-#, (text 'bar' || char '1' || NULL ) IS NULL 2 Answers Sorted by: 9 Use COALESCE to catch and replace NULL values: SELECT f.name AS foo, 'Bazzes: ' COALESCE (stringagg (b.baz, ', '), '') AS bazzes FROM foo f LEFT JOIN bar b ON b.fooid f.id GROUP BY 1 The null-safe concat () is another convenient option as you found yourself, in particular to concatenate multiple values. my code is select into concat ('production.',layername) from concat ('staging.',layername) but there is a problem ERROR: 'concat' is not a known variable LINE 20: select into concat ('production.'layername) from concat ('. test=# SELECT (text 'foo' || NULL) IS NULL 1 I want to create select Query in Postgresql.
#Postgresql string concatenation how to#
How to concatenate columns in a Postgres SELECT?Ĭoncatenating one or more NULL values makes the result NULL.However, the string concatenation operator ( ||) still accepts non-string input, so long as at least one input is of a string type In Postgres, every type has a text representation and can be cast to text. The concatenation operator || can concatenate any string type values, returning text.
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