MySQL: CONCAT with NULL fields
In MySQL,
CONCAT('foo', 'bar', NULL) = NULL
the NULL always wins in MySQL.
If you would rather treat NULL as an empty string, use
CONCAT_WS
Show archive.org snapshot
(concatenation with separator) instead:
CONCAT_WS('', 'foo', 'bar', NULL) = 'foobar'
PostgreSQL
In PostgreSQL the NULL is not viral in CONCAT:
CONCAT('foo', 'bar', NULL) = 'foobar'
Related cards:
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Don't sum up columns with + in a SQL query if NULL-values can be present.
Don't sum up columns with + in a sql-query if NULL-Values can be present.
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MySQL:
mysql> select 1 + 2 + 3;
+-----------+
| 1 + 2 + 3 |
+--...
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