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| docs:mysql:null_values [2007/03/23 15:27] – created billh | docs:mysql:null_values [2008/08/03 00:25] (current) – external edit 127.0.0.1 | ||
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| + | ====== NULL Values ====== | ||
| + | ===== searching for ===== | ||
| + | If you want to search for column values that are NULL, you cannot use an expr = NULL test. The following statement returns no rows, because expr = NULL is never true for any expression: | ||
| + | <code mysql> | ||
| + | mysql> SELECT * FROM my_table WHERE phone = NULL; | ||
| + | </ | ||
| + | |||
| + | To look for NULL values, you must use the IS NULL test. The following statements show how to find the NULL phone number and the empty phone number: | ||
| + | <code mysql> | ||
| + | mysql> SELECT * FROM my_table WHERE phone IS NULL; | ||
| + | mysql> SELECT * FROM my_table WHERE phone = ''; | ||
| + | </ | ||