SQL EXISTS Operator - W3Schools

Trang chủ » Câu Lệnh If Exists Trong Sql » SQL EXISTS Operator - W3Schools

Có thể bạn quan tâm

SQL EXISTS Operator ❮ Previous Next ❯

The SQL EXISTS Operator

The EXISTS operator is used to test for the existence of any record in a subquery.

The EXISTS operator returns TRUE if the subquery returns one or more records.

EXISTS Syntax

SELECT column_name(s) FROM table_name WHERE EXISTS(SELECT column_name FROM table_name WHERE condition);

Demo Database

Below is a selection from the "Products" table in the Northwind sample database:

ProductID ProductName SupplierID CategoryID Unit Price
1 Chais 1 1 10 boxes x 20 bags 18
2 Chang 1 1 24 - 12 oz bottles 19
3 Aniseed Syrup 1 2 12 - 550 ml bottles 10
4 Chef Anton's Cajun Seasoning 2 2 48 - 6 oz jars 22
5 Chef Anton's Gumbo Mix 2 2 36 boxes 21.35

And a selection from the "Suppliers" table:

SupplierID SupplierName ContactName Address City PostalCode Country
1 Exotic Liquid Charlotte Cooper 49 Gilbert St. London EC1 4SD UK
2 New Orleans Cajun Delights Shelley Burke P.O. Box 78934 New Orleans 70117 USA
3 Grandma Kelly's Homestead Regina Murphy 707 Oxford Rd. Ann Arbor 48104 USA
4 Tokyo Traders Yoshi Nagase 9-8 Sekimai Musashino-shi Tokyo 100 Japan

SQL EXISTS Examples

The following SQL statement returns TRUE and lists the suppliers with a product price less than 20:

Example

SELECT SupplierNameFROM SuppliersWHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID = Suppliers.supplierID AND Price < 20); Try it Yourself »

The following SQL statement returns TRUE and lists the suppliers with a product price equal to 22:

Example

SELECT SupplierNameFROM SuppliersWHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID = Suppliers.supplierID AND Price = 22); Try it Yourself » ❮ Previous Next ❯ ★ +1 Sign in to track progress

Từ khóa » Câu Lệnh If Exists Trong Sql