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SELECT not null column from two columns in MySQL?
There are lots of ways to select NOT NULL column from two columns. The syntaxes are as follows:
Case 1: Use IFNULL() function.
The syntax is as follows:
SELECT IFNULL(yourColumnName1,yourColumnName2) as anyVariableName from yourTableName;
Case 2: Use coalesce() function.
The syntax is as follows:
SELECT COALESCE(yourColumnName1,yourColumnName2) as anyVariableName from yourTableName;
Case 3: Use CASE statement.
The syntax is as follows:
SELECT CASE WHEN yourColumnName1 IS NOT NULL THEN yourColumnName1 ELSE yourColumnName2 END AS anyVariableName FROM yourTableName;
Case 4: Use only IF().
The syntax is as follows:
SELECT IF (yourColumnName1 ISNULL,yourColumnName2,yourColumnName1) AS NotNULLValue FROM SelectNotNullColumnsDemo;
To understand the above syntax, let us create a table. The query to create a table is as follows:
mysql> create table SelectNotNullColumnsDemo -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name varchar(20), -> Age int -> , -> PRIMARY KEY(Id) -> ); Query OK, 0 rows affected (0.86 sec)
Insert some records in the table using insert command. The query is as follows:
mysql> insert into SelectNotNullColumnsDemo(Name,Age) values('John',NULL);
Query OK, 1 row affected (0.16 sec)
mysql> insert into SelectNotNullColumnsDemo(Name,Age) values(NULL,23);
Query OK, 1 row affected (0.16 sec)
Display all records from the table using select statement. The query is as follows:
mysql> select *from SelectNotNullColumnsDemo;
The following is the output:
+----+------+------+ | Id | Name | Age | +----+------+------+ | 1 | John | NULL | | 2 | NULL | 23 | +----+------+------+ 2 rows in set (0.00 sec)
Here is the query to select not null values from two columns.
Case 1: IFNULL()
The query is as follows:
mysql> select ifnull(Name,Age) as NotNULLValue from SelectNotNullColumnsDemo;
The following is the output:
+--------------+ | NotNULLValue | +--------------+ | John | | 23 | +--------------+ 2 rows in set (0.00 sec)
Case 2: Coalesce
The query is as follows:
mysql> select coalesce(Name,Age) as NotNULLValue from SelectNotNullColumnsDemo;
The following is the output:
+--------------+ | NotNULLValue | +--------------+ | John | | 23 | +--------------+ 2 rows in set (0.00 sec)
Case 3: CASE
The query is as follows:
mysql> select case -> when Name is not null then Name else Age -> end as NotNULLValue -> from SelectNotNullColumnsDemo;
The following is the output:
+--------------+ | NotNULLValue | +--------------+ | John | | 23 | +--------------+ 2 rows in set (0.00 sec)
Case 4: IF()
The query is as follows:
mysql> select if(Name is NULL,Age,Name) as NotNULLValue from SelectNotNullColumnsDemo;
The following is the output:
+--------------+ | NotNULLValue | +--------------+ | John | | 23 | +--------------+ 2 rows in set (0.00 sec)
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