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)

AmitDiwan

Published on 04-Oct-2019 08:29:30

• Related Questions & Answers
• Display first non-null values with coalesce() in MySQL?
• Fetch maximum value from multiple columns with null and non-null values?
• Perform mathematical calculations in a MySQL table with NULL and NON-NULL values
• Return only the non-empty and non-null values from a table and fill the empty and NULL values with the corresponding column values in MySQL?
• Update all the fields in a table with null or non-null values with MySQL
• Looping in JavaScript to count non-null and non-empty values
• Query non-empty values of a row first in ascending order and then display NULL values
• MySQL query to order by NULL values
• Python Pandas – Propagate non-null values backward
• Python Pandas – Propagate non-null values forward
• Display only NOT NULL values from a column with NULL and NOT NULL records in MySQL
• How to remove null values with PHP?
• How to convert MySQL null to 0 using COALESCE() function?
• MySQL query to order by two fields and NULL values in chronological order?
• Count zero, NULL and distinct values except zero and NULL with a single MySQL query