Tag: Constraint

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Constraint

Constraint : SQL | DEFAULT Constraint

Constraint : This constraint specifies a default value for the column when no value is specified by the user for all new records.IDENTITY and timestamp columns aren’t associated with the default constraint.Add Default Constraing in New TableCREATE TABLE Employee (    ID int NOT NULL,    LastN...

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Constraint

Constraint : SQL | NOT NULL Constraint

Constraint : This constraint tells that we cannot store a null value in a column. That is, if a column is specified as NOT NULL then we will not be able to store null in this particular column any more.By default, if you don’t specify the NOT NULL constraint, SQL Server will allow the column to accepts NULL.Add ...

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Constraint

Constraint : SQL | CHECK Constraint

Constraint : The CHECK constraint is used to limit the values/value range that can be placed in a column.If you define a CHECK constraint on a column it will allow only certain values for this column.If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other c...

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Constraint

Constraint : SQL | Foreign Key Constraint

Constraint : A FOREIGN KEY comprises of single or collection of fields in a table that essentially refers to the PRIMARY KEY in another table. Foreign key constraint ensures referential integrity in the relation between two tables.The table with the foreign key constraint is labeled as the child table, and the t...

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Constraint

Constraint : SQL | Unique Key Constraint

Constraint : Constraints are used to specify the rules concerning data in the table. It can be applied for single or multiple fields in an SQL table during the creation of the table or after creating using the ALTER TABLE command.Unique Key ConstraintUnique Key constraints also identify an individual tuple uniqu...

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Constraint

Constraint : SQL | Primary Key Constraint

Constraint : Constraints are used to specify the rules concerning data in the table. It can be applied for single or multiple fields in an SQL table during the creation of the table or after creating using the ALTER TABLE command.PRIMARY KEY constraintA primary key is a column or a group of columns that uniquely...

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