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)
Published on 04-Oct-2019 11:59:30
