SQL UNIQUE Constraint on ALTER TABLE
Applies to: SQL Server 2008 (10.0.x) and later. Can be specified for FOREIGN KEY constraints and CHECK constraints. If this clause is specified for a constraint, the constraint is not enforced when replication agents perform insert, update, or delete operations. ...
Check constraint - check definition Default constraint - column name and default value definition Rows One rowrepresents one constraint: PK, UK, FK, Check, Default Scope of rows:all constraints Ordered byschema, table name, constraint type Sample results...
当执行 INSERT 和 UPDATE 语句时,CHECK CONSTRAINTS 和规则具有相同的数据验证功能。 当列上存在规则和一个或多个 CHECK 约束时,将验证所有限制。 不能在 text、ntext 或 image 列上定义 CHECK 约束。 其他约束信息 无法使用 DROP INDEX 删除为约束创建的索引;必须使用 ALTER TABLE 来删除约束。 可以使用 ALTER ...
Temporary tables Genuine tables with indexes and constraints, accessible during a session. Multi-use Handling large datasets or when results need multiple references. Subqueries Inline queries without naming, compatible with WHERE clause using IN/EXISTS. Single-use Using IN/EXISTS in a WHERE clause or...
The table declaration includes column definitions, names, data types, and constraints. The only constraint types allowed are PRIMARY KEY, UNIQUE KEY, and NULL. For more information about the syntax, see CREATE TABLE (Transact-SQL), CREATE FUNCTION (Transact-SQL), and DECLARE @local_variable (...
TABLE_CONSTRAINTS (Transact-SQL)Cikk 2023. 03. 01. 11 közreműködő Visszajelzés Applies to: SQL Server Azure SQL Database Azure SQL Managed InstanceReturns one row for each table constraint in the current database. This information schema view returns information about...
DOMAIN_CONSTRAINTS DOMAINS KEY_COLUMN_USAGE PARAMETERS REFERENTIAL_CONSTRAINTS ROUTINE_COLUMNS ROUTINES SCHEMATA TABLE_CONSTRAINTS TABLE_PRIVILEGES TABLES VIEW_COLUMN_USAGE VIEW_TABLE_USAGE VIEWS Gespeicherte Systemprozeduren Systemtabellen Transact-SQL-Referenz (T-SQL) XQuery PDF herunterlad...
ON { partition_scheme | filegroup | "default" } can also be specified in a PRIMARY KEY or UNIQUE constraint. These constraints create indexes. If filegroup is specified, the index is stored in the named filegroup. If "default" is specified, or if ON isn't specified at all, the index ...
The table declaration includes column definitions, names, data types, and constraints. The only constraint types allowed are PRIMARY KEY, UNIQUE KEY, and NULL. For more information about the syntax, see CREATE TABLE (Transact-SQL), CREATE FUNCTION (Transact-SQL), and DECLARE @local_variable (...