Usage of is null in sql
May 01, 2024 pm 10:42 PMIS NULL is an operator in SQL that checks whether a field or expression is a NULL value. The syntax is "Field IS NULL" or "Expression IS NULL". It is commonly used to check whether a field is NULL, compare NULL values to other values, or exclude rows with NULL values from the result set.
Usage of IS NULL in SQL
What is IS NULL?
IS NULL is a SQL operator that checks whether a field or expression is a NULL value. A NULL value means there is no value in the field or the value is unknown.
Syntax
Field IS NULL
Expression IS NULL
## When to use IS NULL?
The IS NULL operator is typically used in the following situations:- Check whether a field is NULL to determine whether certain conditions are true.
- Compare NULL values with other values.
- Exclude rows with NULL values from the result set.
Example
Check if a field is NULL:
SELECT * FROM table_name WHERE field_name IS NULL;
table_name All rows in the table where
field_name is NULL.
Compare NULL values with other values:
SELECT * FROM table_name WHERE field_name = 'John' OR field_name IS NULL;
field_name in the
table_name table that are 'John' or NULL rows.
Exclude rows with NULL values from the result set:
SELECT * FROM table_name WHERE field_name IS NOT NULL;
field_name in the
table_name table Rows that are not NULL.
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