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How to update empty string to NULL in MySQL?
For this, use LENGTH(), since if the length is 0 that would mean the string is empty. After finding, you can set it to NULL using the SET clause in the UPDATE command. Let us first create a table −
mysql> create table DemoTable ( Name varchar(50) ); Query OK, 0 rows affected (0.68 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values('Chris');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable values('');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values('David');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values('');
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 | +-------+ | Chris | | | | David | | | +-------+ 4 rows in set (0.00 sec)
Following is the query to update empty string to NULL −
mysql> update DemoTable set Name=NULL where length(Name)=0; Query OK, 2 rows affected (0.12 sec) Rows matched: 2 Changed: 2 Warnings: 0
Let us check the table records once again −
mysql> select *from DemoTable;
This will produce the following output −
+-------+ | Name | +-------+ | Chris | | NULL | | David | | NULL | +-------+ 4 rows in set (0.00 sec)
Updated on: 01-Oct-2019
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