MySQL provides several functions that are specifically designed to work with NULL
values. These functions allow you to check for NULL
values, handle NULL
values, and perform operations on NULL
values.
Here are some of the commonly used NULL
functions in MySQL:
IS NULL:
This function checks if a value is NULL
. It returns 1
if the value is NULL
, otherwise it returns 0
. For example:
SELECT * FROM table_name WHERE column_name IS NULL;
This query will return all rows in the table_name
where the value of column_name
is NULL
.
IS NOT NULL:
This function checks if a value is not NULL
. It returns 1
if the value is not NULL
, otherwise it returns 0
. For example:
SELECT * FROM table_name WHERE column_name IS NOT NULL;
This query will return all rows in the table_name
where the value of column_name
is not NULL
.
IFNULL:
This function returns the first argument if it is not NULL
, otherwise it returns the second argument. For example:
SELECT IFNULL(column_name, 'NA') FROM table_name;
This query will return the value of column_name
if it is not NULL
, otherwise it will return the string ‘NA’.
COALESCE:
This function returns the first non-NULL
value in a list of arguments. For example:
SELECT COALESCE(column_name1, column_name2, column_name3, 'NA') FROM table_name;
This query will return the first non-NULL
value among column_name1
, column_name2
, and column_name3
, or the string ‘NA’ if all of these columns are NULL
.
NULLIF:
This function returns NULL
if the two arguments are equal, otherwise it returns the first argument. For example:
SELECT NULLIF(column_name, 0) FROM table_name;
This query will return NULL
if the value of column_name
is 0
, otherwise it will return the value of column_name
.
These functions are useful when dealing with NULL
values in your MySQL queries, and can help you handle these values in a more efficient and concise way.