SQL SELECT Statement: SELECT TOP
The SQL SELECT statement is used to retrieve data from a database. The SELECT TOP statement is used to retrieve a specified number of records from the top of a table.
Syntax
The syntax for the SQL SELECT TOP statement is as follows:
SELECT TOP number|percent column1, column2, ... FROM table_name
number: The number of records you want to retrieve from the top of the table.percent: The percentage of records you want to retrieve from the top of the table.column1, column2: The columns that you want to retrieve data from.table_name: The table that you want to retrieve data from.
Example
Let's consider the following table named employees:
| id | name | age |
|---|---|---|
| 1 | John Smith | 30 |
| 2 | Jane Doe | 25 |
| 3 | Bob Jones | 40 |
| 4 | Alice Lee | 35 |
| 5 | Mike Chen | 28 |
If we want to retrieve the top three records from the employees table based on age, we can use the following SQL SELECT TOP statement:
SELECT TOP 3 name, age FROM employees ORDER BY age DESC;
Output
The above example SQL SELECT TOP statement will produce the following output:
| name | age |
|---|---|
| Bob Jones | 40 |
| Alice Lee | 35 |
| John Smith | 30 |
Explanation
In the above example SQL SELECT TOP statement, we have specified that we want to retrieve the top three records from the employees table. We have also specified the columns that we want to retrieve data from (name and age). Finally, we have specified that we want to order the records by age in descending order (ORDER BY age DESC).
Use
The SQL SELECT TOP statement can be useful when you want to retrieve a specific number or percentage of records from the top of a table. This can be particularly useful when working with large tables where you may only need to retrieve a small subset of the total rows.
Important Points
- The SQL SELECT TOP statement can be used with either a specific number of records or a percentage of records.
- If you are using a specific number of records, you must specify an integer value.
- If you are using a percentage of records, you must specify a decimal value between 0 and 1 (e.g. 0.5 for 50%).
- If there are fewer records in the table than the number or percentage specified, the entire table will be returned.
Summary
The SQL SELECT TOP statement is a useful tool for retrieving a specific number or percentage of records from the top of a table. By specifying the columns you want to retrieve data from and the order in which you want the records to be returned, you can quickly and easily retrieve the data you need from large tables.