DevTut

# Limit and Offset

# Limit and Offset relationship

Considering the following users table:

id username
1 User1
2 User2
3 User3
4 User4
5 User5

In order to constrain the number of rows in the result set of a SELECT query (opens new window), the LIMIT clause can be used together with one or two positive integers as arguments (zero included).

# LIMIT clause with one argument

When one argument is used, the result set will only be constrained to the number specified in the following manner:

SELECT * FROM users ORDER BY id ASC LIMIT 2
id username
1 User1
2 User2

If the argument's value is 0, the result set will be empty.

Also notice that the ORDER BY clause may be important in order to specify the first rows of the result set that will be presented (when ordering by another column).

# LIMITclause with two arguments

When two arguments are used in a LIMIT clause:

  • the first argument represents the row from which the result set rows will be presented – this number is often mentioned as an offset, since it represents the row previous to the initial row of the constrained result set. This allows the argument to receive 0 as value and thus taking into consideration the first row of the non-constrained result set.
  • the second argument specifies the maximum number of rows to be returned in the result set (similarly to the one argument's example).

Therefore the query:

SELECT * FROM users ORDER BY id ASC LIMIT 2, 3

Presents the following result set:

id username
3 User3
4 User4
5 User5

Notice that when the offset argument is 0, the result set will be equivalent to a one argument LIMIT clause. This means that the following 2 queries:

SELECT * FROM users ORDER BY id ASC LIMIT 0, 2

SELECT * FROM users ORDER BY id ASC LIMIT 2

Produce the same result set:

id username
1 User1
2 User2

# OFFSET keyword: alternative syntax

An alternative syntax for the LIMIT clause with two arguments consists in the usage of the OFFSET keyword after the first argument in the following manner:

SELECT * FROM users ORDER BY id ASC LIMIT 2 OFFSET 3

This query would return the following result set:

id username
3 User3
4 User4

Notice that in this alternative syntax the arguments have their positions switched:

  • the **first** argument represents the number of rows to be returned in the result set;
  • the **second** argument represents the offset.

    • # Syntax

  • SELECT column_1 [, column_2 ]
    FROM table_1
    ORDER BY order_column
    LIMIT row_count [OFFSET row_offset]
  • SELECT column_1 [, column_2 ]
    FROM table_1
    ORDER BY order_column
    LIMIT [row_offset,] row_count

    • # Remarks

    "Limit" could mean "Max number of rows in a table".

    "Offset" mean pick from row number (not to be confused by primary key value or any field data value)

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