DBCC CHECKCONSTRAINTS (Transact-SQL)

 

THIS TOPIC APPLIES TO:yesSQL Server (starting with 2008)noAzure SQL DatabasenoAzure SQL Data Warehouse noParallel Data Warehouse

Checks the integrity of a specified constraint or all constraints on a specified table in the current database.

Topic link icon Transact-SQL Syntax Conventions

  
DBCC CHECKCONSTRAINTS  
[   
    (   
    table_name | table_id | constraint_name | constraint_id   
    )  
]  
    [ WITH   
    [ { ALL_CONSTRAINTS | ALL_ERRORMSGS } ]  
    [ , ] [ NO_INFOMSGS ]   
    ]  

table_name | table_id | constraint_name | constraint_id
Is the table or constraint to be checked. When table_name or table_id is specified, all enabled constraints on that table are checked. When constraint_name or constraint_id is specified, only that constraint is checked. If neither a table identifier nor a constraint identifier is specified, all enabled constraints on all tables in the current database are checked.

A constraint name uniquely identifies the table to which it belongs. For more information, see Database Identifiers.

WITH
Enables options to be specified

ALL_CONSTRAINTS
Checks all enabled and disabled constraints on the table if the table name is specified or if all tables are checked; otherwise, checks only the enabled constraint. ALL_CONSTRAINTS has no effect when a constraint name is specified.

ALL_ERRORMSGS
Returns all rows that violate constraints in the table that is checked. The default is the first 200 rows.

NO_INFOMSGS
Suppresses all informational messages.

DBCC CHECKCONSTRAINTS constructs and executes a query for all FOREIGN KEY constraints and CHECK constraints on a table.

For example, a foreign key query is of the following form:

SELECT <columns>  
FROM <table_being_checked> LEFT JOIN <referenced_table>  
    ON <table_being_checked.fkey1> = <referenced_table.pkey1>   
    AND <table_being_checked.fkey2> = <referenced_table.pkey2>  
WHERE <table_being_checked.fkey1> IS NOT NULL   
    AND <referenced_table.pkey1> IS NULL  
    AND <table_being_checked.fkey2> IS NOT NULL  
    AND <referenced_table.pkey2> IS NULL  

The query data is stored in a temp table. After all requested tables or constraints have been checked, the result set is returned.

DBCC CHECKCONSTRAINTS checks the integrity of FOREIGN KEY and CHECK constraints but does not check the integrity of the on-disk data structures of a table. These data structure checks can be performed by using DBCC CHECKDB and DBCC CHECKTABLE.

Applies to: SQL Server 2016 through SQL Server 2016.

If table_name or table_id is specified and it is enabled for system versioning, DBCC CHECKCONSTRAINTS also performs temporal data consistency checks on the specified table. When NO_INFOMSGS is not specified, this command will return each consistency violation in the output on a separate line. The format of the output will be ([pkcol1], [pkcol2]..) = (<pkcol1_value>, <pkcol2_value>…) AND <what is wrong with temporal table record>.

CheckAdditional info in output if check failed
PeriodEndColumn ≥ PeriodStartColumn (current)[sys_end] = '{0}' AND MAX(DATETIME2) = '9999-12-31 23:59:59.99999'
PeriodEndColumn ≥ PeriodStartColumn (current, history)[sys_start] = '{0}' AND [sys_end] = '{1}'
PeriodStartColumn < current_utc_time (current)[sys_start] = '{0}' AND SYSUTCTIME
PeriodEndColumn < current_utc_time (history)[sys_end] = '{0}' AND SYSUTCTIME
Overlaps(sys_start1, sys_end1) , (sys_start2, sys_end2) for two overlapping records.

If there are more than 2 overlapping records, output will have multiple rows each showing a pair of overlaps.

There is no way to specify constraint_name or constraint_id in order to run only temporal consistency checks.

DBCC CHECKCONSTRAINTS return a rowset with the following columns.

Column nameData typeDescription
Table NamevarcharName of the table.
Constraint NamevarcharName of the constraint that is violated.
WherevarcharColumn value assignments that identify the row or rows violating the constraint.

The value in this column can be used in a WHERE clause of a SELECT statement querying for rows that violate the constraint.

Requires membership in the sysadmin fixed server role or the db_owner fixed database role.

A. Checking a table

The following example checks the constraint integrity of the table Table1 in the AdventureWorks database.

USE AdventureWorks2012;  
GO  
CREATE TABLE Table1 (Col1 int, Col2 char (30));  
GO  
INSERT INTO Table1 VALUES (100, 'Hello');  
GO  
ALTER TABLE Table1 WITH NOCHECK ADD CONSTRAINT chkTab1 CHECK (Col1 > 100);  
GO  
DBCC CHECKCONSTRAINTS(Table1);  
GO  

B. Checking a specific constraint

The following example checks the integrity of the CK_ProductCostHistory_EndDate constraint.

USE AdventureWorks2012;  
GO  
DBCC CHECKCONSTRAINTS ('Production.CK_ProductCostHistory_EndDate');  
GO  

C. Checking all enabled and disabled constraints on all tables

The following example checks the integrity of all enabled and disabled constraints on all tables in the current database.

DBCC CHECKCONSTRAINTS WITH ALL_CONSTRAINTS;  
GO  

DBCC CHECKDB (Transact-SQL)
DBCC CHECKTABLE (Transact-SQL)
DBCC (Transact-SQL)

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