Does it make sense to use "LIMIT 1" in the query "SELECT 1 ..."?

Yes, you can use LIMIT 1 in SELECT 1.

Suppose you are using SELECT 1 and your table has billions of records. In this case it prints 100 million times.

The syntax of SELECT 1 is as follows −

SELECT 1 FROM yourTableName;

Suppose, you are using LIMIT 1 and your table has billions of records. This case, it will print 1 only once.

The syntax of SELECT 1 with LIMIT 1 is as follows −

SELECT 1 FROM yourTableName LIMIT 1;

To understand the above syntax, let us create a table. The query to create a table is as follows −

mysql> create table Select1AndLimit1Demo
   -> (
   -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   -> Name varchar(20)
   -> );
Query OK, 0 rows affected (1.99 sec)

Use insert command to insert some records in the table. The query is as follows −

mysql> insert into Select1AndLimit1Demo(Name) values('John');
Query OK, 1 row affected (0.21 sec)
mysql> insert into Select1AndLimit1Demo(Name) values('Carol');
Query OK, 1 row affected (0.14 sec)
mysql> insert into Select1AndLimit1Demo(Name) values('Sam');
Query OK, 1 row affected (0.11 sec)
mysql> insert into Select1AndLimit1Demo(Name) values('Bob');
Query OK, 1 row affected (0.18 sec)
mysql> insert into Select1AndLimit1Demo(Name) values('David');
Query OK, 1 row affected (0.14 sec)
mysql> insert into Select1AndLimit1Demo(Name) values('Mike');
Query OK, 1 row affected (0.20 sec)
mysql> insert into Select1AndLimit1Demo(Name) values('Maxwell');
Query OK, 1 row affected (0.11 sec)

Display all records from the table using a select statement. The query is as follows −

mysql> select *from Select1AndLimit1Demo;

Output

+----+---------+
| Id | Name    |
+----+---------+
|  1 | John    |
|  2 | Carol   |
|  3 | Sam     |
|  4 | Bob     |
|  5 | David   |
|  6 | Mike    |
|  7 | Maxwell |
+----+---------+
7 rows in set (0.00 sec)

Above, we have a table with 7 records. Therefore, the output is 7 times 1.

Let us now see the case of SELECT 1 with LIMIT 1. The query is as follows −

mysql> select 1 from Select1AndLimit1Demo;

The following is the output result, only showing the value 1 once −

+---+
| 1 |
+---+
| 1 |
| 1 |
| 1 |
| 1 |
| 1 |
| 1 |
| 1 |
+---+
7 rows in set (0.00 sec)

Above, our table has 7 records. We get 1 times 1 because we used LIMIT 1.

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