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
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. ...
一律傳回 NO。 INITIALLY_DEFERRED varchar(2) 指定條件約束檢查是否一開始延遲。 一律傳回 NO。 另請參閱 系統檢視 (Transact-SQL) 資訊架構檢視 (Transact-SQL) sys.objects (Transact-SQL) sys.key_constraints (Transact-SQL) sys.check_constraints (Transact-SQL) sys.tables (Transact-...
Constraints can be categorized intocolumn levelortable level. The column-level constraints are implemented to a column, and the table-level constraints are implemented to the whole table. Theuser_constraintsare utilized to display the names of the constraints in the database. Theall_constraintsprovid...
查看information_schema.TABLE_CONSTRAINTS视图 查看information_schema.CHECK_CONSTRAINTS视图 constraint_name约束名称,最多包含 64 个字符。 约束名称的开头结尾中间都允许有空格,但需要用"`"标识名称的开头和结尾。 约束名称可以包含特殊字符"$"。 如果约束名称为保留字,需要用"`"标识,否则会报错。
ALTER TABLE table_constraints メモリ最適化テーブルの構文 syntaxsql コピー ALTER TABLE { database_name.schema_name.table_name | schema_name.table_name | table_name } { ALTER COLUMN column_name { [ type_schema_name. ] type_name [ ( { precision [ , scale ] } ) ] [ COLLATE coll...
FOREIGN KEY constraints can reference only columns that are PRIMARY KEY or UNIQUE constraints in the referenced table or columns referenced in a UNIQUE INDEX on the referenced table. Foreign keys on computed columns must also be marked PERSISTED. [ [ schema_name. ] referenced_table_name ] The ...
Create a table with constraints Now, let us understand how we can create a table with a constraint. A table can have the following constraints. NOT NULL: This constraint ensures that a query does not insert a NULL value in a column on which the constraint has been created. ...
You can do to a temporary table the same things you do with regular tables. You can SELECT, INSERT, UPDATE, DELETE, and TRUNCATE them. And you can also use INDEX and add constraints. And finally, you can use DROP to erase them. ...