DBCC CHECKCONSTRAINTS (Transact-SQL)

Cikk
12/29/2022

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

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

Syntax

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

Arguments

table_name | table_id | constraint_name | constraint_id

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 a table identifier or a constraint identifier isn't 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.

Remarks

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 doesn't 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 (13.x) and later versions

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 isn't 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>.

Check	Additional 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 two overlapping records, output will have multiple rows each showing a pair of overlaps.

You can't specify constraint_name or constraint_id in order to run only temporal consistency checks.

Result sets

DBCC CHECKCONSTRAINTS return a rowset with the following columns.

Column name	Data type	Description
Table Name	varchar	Name of the table.
Constraint Name	varchar	Name of the constraint that is violated.
Where	varchar	Column 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.

DBCC CHECKCONSTRAINTS isn't guaranteed to find all constraint violations. If a single row violates multiple constraints, only the WHERE clause for the first violation is listed. Unless another row exists with the same combination of values that produce the violation, and has that violation as the first violation found, the combination of values will be missing from the returned result set. You may have to run DBCC CHECKCONSTRAINTS and fix problems several times before finding all constraint violations in the database.

Permissions

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

Examples

A. Check a table

The following example checks the constraint integrity of the table Table1 in the AdventureWorks2022 database.

USE AdventureWorks2022;
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. Check a specific constraint

The following example checks the integrity of the CK_ProductCostHistory_EndDate constraint.

USE AdventureWorks2022;
GO
DBCC CHECKCONSTRAINTS ('Production.CK_ProductCostHistory_EndDate');
GO

C. Check 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

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