Whenever you define a constraint, your RDBMS generates a name for it automatically. This name is used to reference the constraint in error messages in commands used to manage constraints. Sometimes, though, it’s convenient for database administrators to provide their own name for a constraint. ...
SQL Copy Here we get the constraints name that we have created. Now we are able to drop the constraints by using the above name. alter table STUDENT_DETAILS drop constraint DF__STUDENT_D__IS_RE__3846C6FF SQL Copy Now we are able to drop the column by using the below query. alter ...
ADD CONSTRAINT FK_ConstraintName FOREIGN KEY (ForeignKeyColumn) REFERENCES MainTable (PrimaryKeyColumn); In this example, you need to drop the foreign key constraints before truncating the main table and then recreate them afterward. Example 3: TRUNCATE with Identity ColumnsIf your table has an ide...
If you want to remove an existing table from a database, use the statementDROP TABLEwith the name of the table. In this example, we first wrote the commandDROP TABLEfollowed by the table nameproduct. That’s all you need to do. This command removes the table’s data, the table structu...
How to change columns in a unique constraint Over time you may want to add or remove columns from a unique constraint. As with check constraints, you'll need to create a new constraint and drop the original. The process for doing this online has an extra step: ...
modified as long as the referencing object exists. A schema-bound dependency is created when a view or user-defined function is created by using the WITH SCHEMABINDING clause, or when a table references another object through a CHECK or DEFAULT constraint or in the definition of a computed ...
tab_con.TABLE_NAME + N'] DROP ['+ ref_con.CONSTRAINT_NAME + N'];' FROMINFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS ref_con LEFTJOININFORMATION_SCHEMA.TABLE_CONSTRAINTS tab_con ONtab_con.CONSTRAINT_NAME = ref_con.CONSTRAINT_NAME OPEN@CURSORFETCHNEXTFROM@CURSORINTO@SQL ...
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Listing 4. Clustering on the UNIQUE constraint. declare @t table (OrderID int primary key nonclustered, RequiredDate datetime not null, ShippedDate datetime null, unique clustered (RequiredDate, OrderID)) This time, you get one more logical read and a very slight drop in query cost to 0.069...
You can also achieve the same effect using a combination of INSTEAD OF DELETE and a CHECK constraint based on a trivial false condition like say 1=0 for INSERT/UPDATE operations. Method 4 : Adding a Columnstore Index on the Table Another method which can be implemented in...