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Can a check constraint be applied to multiple columns?
You can also apply a single CHECK constraint to multiple columns by creating it at the table level. For example, a multiple-column CHECK constraint could be used to confirm that any row with a country_region column value of USA also has a two-character value in the state column. This allows for multiple conditions to be checked in one location.
How to create constraint such as only one of two?
I have a table in SQL server where the users need to enter data in either of two columns. That is, One of the two must have data inputted but at the same time i don’t want to allow users to input in both columns.
How to require one of two columns in SQL Server?
I’m using SQL Server 2008 R2 and would like to make one of two columns required on a table; in other words, if the user provides a value for one, the other isn’t required but the user can provide a value for both. How do you do this using check constraints?
What are unique constraints and check constraints in SQL Server?
UNIQUE constraints and CHECK constraints are two types of constraints that can be used to enforce data integrity in SQL Server tables. These are important database objects. This topic contains the following sections.
What happens when you add a unique constraint to a table?
When a UNIQUE constraint is added to an existing column or columns in the table, by default, the Database Engine examines the existing data in the columns to make sure all values are unique. If a UNIQUE constraint is added to a column that has duplicated values, the Database Engine returns an error and does not add…
What are the limitations of a check constraint?
Limitations of CHECK Constraints. The CHECK constraint being added specifies that there must be at least one row in table CheckTbl. However, because there are no rows in the table against which to check the condition of this constraint, the ALTER TABLE statement succeeds. CHECK constraints are not validated during DELETE statements.