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Only update the MySQL field if the field contains null or 0?
For this, set conditions using MySQL IF(). Let us first create a table −
mysql> create table DemoTable1592 -> ( -> StudentMarks int -> ); Query OK, 0 rows affected (0.76 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable1592 values(56); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1592 values(NULL); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1592 values(98); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1592 values(0); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1592 values(75); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable1592 values(NULL); Query OK, 1 row affected (0.11 sec)
Display all records from the table using select statement −
mysql> select * from DemoTable1592;
This will produce the following output −
+--------------+ | StudentMarks | +--------------+ | 56 | | NULL | | 98 | | 0 | | 75 | | NULL | +--------------+ 6 rows in set (0.00 sec)
Here is the query to only update the field if it contains null or 0 −
mysql> update DemoTable1592 set StudentMarks=if(StudentMarks IS NULL or StudentMarks=0,33,StudentMarks); Query OK, 3 rows affected (0.17 sec) Rows matched: 6 Changed: 3 Warnings: 0
Let us check the table records once again −
mysql> select * from DemoTable1592;
This will produce the following output −
+--------------+ | StudentMarks | +--------------+ | 56 | | 33 | | 98 | | 33 | | 75 | | 33 | +--------------+ 6 rows in set (0.00 sec)
Updated on: 16-Dec-2019
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