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Learn how to test for NULL values in SQL using the IS NULL and IS NOT NULL operators. A NULL value is a field with no value, different from zero or spaces.
3 wrz 2024 · Replaces NULL with the specified replacement value. Transact-SQL syntax conventions. Syntax ISNULL ( check_expression , replacement_value ) Arguments check_expression. The expression to be checked for NULL. check_expression can be of any type. replacement_value. The expression to be returned if check_expression is NULL.
Use the LEN function to check for null or empty values. You can just use LEN(@SomeVarcharParm) > 0. This will return false if the value is NULL, '', or ' '. This is because LEN(NULL) returns NULL and NULL > 0 returns false. Also, LEN(' ') returns 0. See for yourself run:
Learn what NULL means in SQL and how to use the IS NULL and IS NOT NULL operators to test if an expression is NULL or not. See examples with the employees table and compare NULL with other values.
6 cze 2024 · We can use the function NULLIF to compare and check if the column contains null or empty values: SELECT id, name FROM Department WHERE NULLIF(TRIM(code), '') IS NULL; The NULLIF function evaluates its two arguments, returning NULL if they are equal.
19 maj 2021 · Learn how to handle SQL NULL values with IS NULL, IS NOT NULL, ISNULL, COALESCE, and other functions. See examples of queries, problems, and solutions related to NULL values.
3 wrz 2024 · To determine whether an expression is NULL, use IS NULL or IS NOT NULL instead of comparison operators (such as = or !=). Comparison operators return UNKNOWN when either or both arguments are NULL. Examples
