#foreign key constraint in sql server

[bigdatansql]

Add a foreign key constraint on the existing table - SQL Server

While it is best to create and build the link between tables before the data flow begins, new tables or other existing tables may need to be linked due to a change in plans.

While it is best to create and build the link between tables before the data flow begins, new tables or other existing tables may need to be linked due to a change in plans. In such scenarios using ALTER statement, foreign keys can be created as shown below. ALTER TABLE tbOrderDetailsADD CONSTRAINT FK_OrderID_tbOrderDetails FOREIGN KEY (OrderID)REFERENCES tbOrders (OrderID)ON DELETE CASCADEON…

View On WordPress

[bigdatansql]

Define Foreign Key In Different Ways - SQL Server

A foreign key (FK) is a column or group of columns used to create and enforce a link between data in two tables in order to control the data that can be put in the foreign key table. When the column or columns that carry the primary key value for one tabl

A foreign key (FK) is a column or group of columns used to create and enforce a link between data in two tables in order to control the data that can be put in the foreign key table. When the column or columns that carry the primary key value for one table are referenced by the column or columns in another table, a link is formed between the two tables. In the second table, this column becomes a…

View On WordPress

[bigdatansql]

Referential Integrity Constraints

A foreign key must match a primary key or be null in order to maintain referential integrity. In other words, every column in a base table that is declared a foreign key can only contain null values, values from a parent table's primary key, or values fro

A foreign key must match a primary key or be null in order to maintain referential integrity. In other words, every column in a base table that is declared a foreign key can only contain null values, values from a parent table’s primary key, or values from a candidate key for referential integrity to hold in a relational database. This will help you maintain data quality and ensure that no data…

View On WordPress