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How does COALESCE order results with NULL and NON-NULL values?
The COALESCE() finds the NON-NULL value first If it finds the same in the beginning, then it returns, otherwise moves ahead to check NON-NULL value.
Let us first create a table −
mysql> create table DemoTable ( Number1 int, Number2 int ); Query OK, 0 rows affected (5.48 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values(100,200); Query OK, 1 row affected (0.40 sec) mysql> insert into DemoTable values(NULL,50); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(10,NULL); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values(NULL,NULL); Query OK, 1 row affected (0.08 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+---------+---------+ | Number1 | Number2 | +---------+---------+ | 100 | 200 | | NULL | 50 | | 10 | NULL | | NULL | NULL | +---------+---------+ 4 rows in set (0.00 sec)
Following is the query to order records with COALESCE −
mysql> select coalesce(Number1,Number2) AS NON_NULL_ARGUMENT_FIRST from DemoTable;
This will produce the following output −
+-------------------------+ | NON_NULL_ARGUMENT_FIRST | +-------------------------+ | 100 | | 50 | | 10 | | NULL | +-------------------------+ 4 rows in set (0.00 sec)
Updated on: 04-Oct-2019
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