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Can MySQL automatically convert empty strings to NULL?
You need to use NULLIF() function from MySQL. The syntax is as follows:
SELECT NULLIF(yourCoumnName,’ ’) as anyVariableName from yourTableName;
In the above syntax, if you compare empty string( ‘ ‘) to empty string( ‘ ‘), the result will always be NULL. However, if you compare with NULL to empty string( ‘ ‘) then also the result will always be NULL.
To understand the above syntax, let us create a table. The query to create a table is as follows:
mysql> create table ConvertEmptyStringToNULL -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name varchar(20), -> PRIMARY KEY(Id) -> ); Query OK, 0 rows affected (0.63 sec)
Insert some records in the table using insert command. The query is as follows:
mysql> insert into ConvertEmptyStringToNULL(Name) values('John');
Query OK, 1 row affected (0.22 sec)
mysql> insert into ConvertEmptyStringToNULL(Name) values('');
Query OK, 1 row affected (0.15 sec)
mysql> insert into ConvertEmptyStringToNULL(Name) values(NULL);
Query OK, 1 row affected (0.14 sec)
mysql> insert into ConvertEmptyStringToNULL(Name) values('');
Query OK, 1 row affected (0.21 sec)
mysql> insert into ConvertEmptyStringToNULL(Name) values('Carol');
Query OK, 1 row affected (0.13 sec)
mysql> insert into ConvertEmptyStringToNULL(Name) values(NULL);
Query OK, 1 row affected (0.70 sec)Display all records from the table using select statement. The query is as follows:
mysql> select *from ConvertEmptyStringToNULL;
The following is the output:
+----+-------+ | Id | Name | +----+-------+ | 1 | John | | 2 | | | 3 | NULL | | 4 | | | 5 | Carol | | 6 | NULL | +----+-------+ 6 rows in set (0.00 sec)
Here is the query to convert empty string to NULL:
mysql> select NULLIF(Name,'') as EmptyStringNULL from ConvertEmptyStringToNULL;
The following is the output displaying NULL in place of empty string:
+------------------+ | EmptyStringNULL | +------------------+ | John | | NULL | | NULL | | NULL | | Carol | | NULL | +------------------+ 6 rows in set (0.00 sec)
Updated on: 30-Jul-2019
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