I have explained how we can create CHECKĬonstraints using CREATE TABLE statement. In this article, we learned about the Postgres check constraint. To do that, expand DemoDatabase □ Expand Schemas □ Expand public □ Expand Tables □ Expand Constraints.Īs you can see, three constraints have been created on the tblPurchaseOrder table. On nname = nstraint_nameĪnd namespace.nspname = nstraint_schemaĪlternatively, you can use the pgAdmin4 tool to view the constraints. Left join information_nstraint_column_usage columnusage Join pg_class class on nrelid = class.oid Join pg_namespace namespace on namespace.oid = nnamespace To view the list of CHECK constraints created on a table, we can use the following queryĬolumnusage.table_schema as table_schema, Let us insert the record with the value of the Orderd_Date higher than the Current_date. First, let us insert the record with the value of Orderd_Date=’.’ Let us test theĬonstraint by inserting records. We can specify the definition of the CHECK constraint under the definition sub-menu.Ĭlick on the Save button to create the constraint and close the dialog box. To fulfill the above condition, the definition of the CHECK condition must be the following.ĬHECK (orderd_date between Current_date-INTEGER ’10’ AND Current_date) The value of the Orderd_Date column must not be greater than the current date and time For example, if today is and the user tries to insert the value of Orderd_Date as, the query must return an error When the user executes the INSERT statement, the value of Orderd_Date should not be older than ten days. The CHECK constraint is a combination of two conditions: Now, we want to create a CHECK constraint on the tblPurchaseOrder table. You can specify the desired name of the constraint in the name textbox. Click on the (+) sign and then click on the edit row button.Īnother submenu opens. On the dialog box, click on Constraints, and in the sub-menu,Ĭlick on Check. Right-click on DemoDatabase □ Expand Schemas □ Expand public □ Expand Tables □ Right-click on tables □ Select Properties.Ī dialog box to configure the table properties opens. To view the objects, expand Servers □ Expand PostgreSQL13 □ Expand Databases. You can view the list of the installed servers and objects in the Browser pan. Specify the master password to connect to the PostgreSQL. To create a CHECK constraint, launch pgAdmin4. Now, let us insert a record with Product_Cost 10 days, the query must return an error. When we add a record with the Product_Cost 0) We want to add a CHECK constraint on the Product_Cost column of the tblPurchaseOrder table. The CHECK condition must be specified between the parentheses Condition: Specify the CHECK condition.The constraint name must be specified after ADD CONSTRAINT expression constraint_name: Specify the desired constraint name.tbl_name: Specify the table name which contains the column on which you want to add the CHECK CONSTRAINT.The syntax to add the constraint is as the following.ĪLTER TABLE tbl_name ADD CONSTRAINT constraint_name CHECK (condition) We can add a constraint by using ALTER TABLE statement. Following is the pattern:Ĭreate table tbl_name(col_1 datatype, Col_2 data_type CONSTRAINT constraint_name (Check_condition))Īdd constraint using ALTER TABLE statement We can specify the constraint name after specifying the CONSTRAINT expression. We can specify the name of the constraint in the CREATE TABLE statement.While creating a new table, if we define a CHECK constraint without specifying the name, the PostgreSQL assigns a name that follows _check naming convention.Let us try to insert a record with order_quantity =0. (1,’PROD0001′,5,500,’nisarg.upadhyay’, ‘’)Īs you can see, the record has been added successfully. (orderID, Product_code, Order_Qty, Product_Cost, UserID, Orderd_Date) Now, let us try to add a record with the order_quantity > 0. Inserts the record with the order_quantity =0, then it should throw an error. The CHECK constraint checks that the value of the order_quantity column must be greater than zero.
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