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Updating blank cells to NULL will cause all cells to be NULL in MySQL?
To update only blank cells to NULL, use NULLIF() in MySQL. Let us first create a table −
mysql> create table DemoTable ( Name varchar(50) ); Query OK, 0 rows affected (1.73 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable values(''); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values('David'); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable values(''); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.15 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+-------+ | Name | +-------+ | Mike | | | | David | | | | Mike | +-------+ 5 rows in set (0.00 sec)
Following is the query to update only blank cells to NULL −
mysql> update DemoTable set Name=NULLIF(Name,''); Query OK, 2 rows affected (0.19 sec) Rows matched: 5 Changed: 2 Warnings: 0
Let us check the table records once again −
mysql> select *from DemoTable;
This will produce the following output −
+-------+ | Name | +-------+ | Mike | | NULL | | David | | NULL | | Mike | +-------+ 5 rows in set (0.00 sec)
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