Explanation of SQL TOP clause

SQL TOP plays an important role in advanced operations of the database, and this article will explain it.

TOP clause

The TOP clause is used to specify the number of records to be returned.

The TOP clause is very useful for large tables with thousands of records.

Note: Not all database systems support the TOP clause.

SQL Server syntax:

SELECT TOP number|percent column_name(s)
FROM table_name

MySQL and Oracle The SQL SELECT TOP is equivalent

MySQL Syntax

SELECT column_name(s)
FROM table_name
LIMIT number

Example

SELECT *
FROM Persons
LIMIT 5

Oracle Syntax

SELECT column_name(s)
FROM table_name
WHERE ROWNUM <= number

Example

SELECT *
FROM Persons
WHERE ROWNUM <= 5

SQL TOP Example

Now, we want to select the first two records from the "Persons" table above.

We can use the following SELECT statement:

SELECT TOP 2 * FROM Persons

This article provides a relevant explanation of the SQL TOP clause. For more learning materials, please pay attention to the php Chinese website.

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