MySQL SELECT from table A that does not exist in table B using JOINS?

To SELECT from table A that does not exist in table B, you can use left join. Following is the syntax −

select yourTableNameA.*
from yourTableNameA left join yourTableNameB on yourTableNameA.yourColumnName =
yourTableNameB.yourColumnName
where yourTableNameB.yourColumnName
IS NULL;

Let us first create a table. Following is the query −

<table_A>

mysql> create table table_A
   -> (
   -> Value int
   -> );
Query OK, 0 rows affected (1.10 sec)

Following is the query to insert records in the table using insert command −

mysql> insert into table_A values(10);
Query OK, 1 row affected (0.32 sec)

mysql> insert into table_A values(15);
Query OK, 1 row affected (0.10 sec)

mysql> insert into table_A values(35);
Query OK, 1 row affected (0.21 sec)

mysql> insert into table_A values(45);
Query OK, 1 row affected (0.13 sec)

Following is the query to display all records from the table using select statement −

mysql> select *from table_A;

This will produce the following output −

+-------+
| Value |
+-------+
| 10    |
| 15    |
| 35    |
| 45    |
+-------+
4 rows in set (0.00 sec)

Let us create another table. Following is the query −

<table_B>

mysql> create table table_B
   -> (
   -> Value int
   -> );
Query OK, 0 rows affected (0.51 sec)

Following is the query to insert some records in the table using insert command −

mysql> insert into table_B values(10);
Query OK, 1 row affected (0.18 sec)

mysql> insert into table_B values(20);
Query OK, 1 row affected (0.12 sec)

mysql> insert into table_B values(35);
Query OK, 1 row affected (0.23 sec)

mysql> insert into table_B values(60);
Query OK, 1 row affected (0.12 sec)

Following is the query to display all records from the table using a select statement −

mysql> select *from table_B;

This will produce the following output −

+-------+
| Value |
+-------+
| 10    |
| 20    |
| 35    |
| 60    |
+-------+
4 rows in set (0.00 sec)

Following is the query to select from table A that does not exist in table B with LEFT JOIN −

mysql> select table_A.*
   -> from table_A left join table_B on table_A.Value = table_B.Value
   -> where table_B.Value IS NULL;

This will produce the following output −

+-------+
| Value |
+-------+
| 15    |
| 45    |
+-------+
2 rows in set (0.04 sec)

Smita Kapse

Published on 15-Apr-2019 11:38:30

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