![]() ![]() It's about concatenation with an actual NULL value, with the concatenation operator || and still getting a non-null result. The function does not add the separator at the end of the string. ![]() Syntax: Consider the following syntax of the CONCAT () function: CONCAT ( string1, string2. Note: CASE or COALESCE catching NULL values are typically good style, but that's not what this question is about. The PostgreSQL STRINGAGG () function is an aggregate function that concatenates a list of strings and places a separator between them. The PostgreSQL CONCAT () function ignores the NULL input if passed, which means we can concatenate the strings even if one of the input strings from a list of arguments provided is NULL. 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. Suppose we want to concatenate the given string and the number. In other words, how is this possible? test=# SELECT col IS NULL AS col_is_null Suppose we have a string Postgres and the number 14.4. Is it possible to concatenate a text and a NULL value and get a non-null result? Test-#, (NULL::bigint || text 'baz') IS NULL Test-#, (text 'bar' || char '1' || NULL ) IS NULL The concat, concatws and format functions are variadic, so it is possible to pass the values to be concatenated or formatted as an array marked with the VARIADIC keyword (see Section 35.4.5).The arrays elements are treated as if they were separate ordinary arguments to the function. test=# SELECT (text 'foo' || NULL) IS NULL 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 PostgreSQL, the CONCAT function is used to concatenate two or more strings into one. In Postgres, every type has a text representation and can be cast to text. You can concatenate together multiple strings to make a single string. The concatenation operator || can concatenate any string type values, returning text. ![]()
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