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Learn how to test for NULL values in MySQL using the IS NULL and IS NOT NULL operators. A NULL value is a field with no value, different from zero or spaces.
6 de dic. de 2016 · SELECT ifnull(nullif(field1,''),'empty or null') AS field1 FROM tablename; How it works: nullif is returning NULL if field is an empty string, otherwise returns the field itself. This has both the cases covered (the case when field is NULL and the case when it's an empty string).
Here’s the basic syntax of the IS NULL operator: value IS NULL Code language: SQL (Structured Query Language) (sql) If the value is NULL, the expression returns true. Otherwise, it returns false. Note that MySQL does not have a built-in BOOLEAN type. It uses the TINYINT(1) to represent the BOOLEAN values i.e., true means 1 and false means 0.
Learn how to test, compare and handle NULL values in MySQL, which means “a missing unknown value”. See examples, rules and common errors when working with NULL.
Description. The MySQL IS NULL Condition is used to test for a NULL value in a SELECT, INSERT, UPDATE, or DELETE statement. Syntax. The syntax for the IS NULL Condition in MySQL is: expression IS NULL. Parameters or Arguments. expression. The value to test if it is a NULL value. Note. If expression is a NULL value, the condition evaluates to TRUE.
In MySQL, a NULL value means unknown. A NULL value is different from zero ( 0) or an empty string ''. A NULL value is not equal to anything, even itself. If you compare a NULL value with another NULL value or any other value, the result is NULL because the value of each NULL value is unknown.
