To remove a constraint, use theDROP CONSTRAINTclause in theALTER TABLEstatement. If you wish to drop the unique constraint on the “Email” column: ALTER TABLE Customers DROP CONSTRAINT UQ_Email; 4. Renaming Tables TheALTERcommand allows you to rename a table easily. Suppose you want to renam...
MS SQL Server Operators: UNIQUE ADD CONSTRAINT ALTER TABLE Problem: You would like to make a column unique in a given table in a database. Example: We would like to make the columnnameunique in the tableproduct. The query below presents one way to do it. ...
Thealter table ... modify constraintcommand only supports enabling or disabling it. If you want to change a constraint, you need to drop the current one and recreate it with the new criteria: Easy enough. But there's a problem. There's a period where neither the old nor the new constra...
When designing an SQL database, there may be cases where you want to impose restrictions on what data can be added to certain columns in a table. SQL makes this possible through the use ofconstraints. After applying a constraint to a column or table, any attempts to add data to the colu...
3. To DROP a Column in SQL Another method to use a DROP command is to alter a table to drop a specific column or multiple specific columns as needed. For this, we can use the “DROP COLUMN” command. In MySQL, the “DROP COLUMN” command is used along with the “ALTER TABLE” co...
Write a SQL query to add a unique constraint to a column in an existing table. Solution: -- Add a unique constraint to the "Name" column to ensure no duplicate names.ALTERTABLEEmployees-- Specify the table to modify.ADDCONSTRAINTUC_NameUNIQUE(Name);-- Ensure all names are unique...
Drop the Primary Key in SQL Server To Drop the Primary Key, we use the below syntax. It does not matter if the Primary Key was on single or multiple columns. ALTER TABLE <schema_name>. DROP CONSTRAINT <constraint_name> ; To drop the ...
ALTER TABLE table_name ADD column_name data_type constraint Parameters: table_name:The existing table’s name. column_name:The new column’s name. data_type:The new column’s data type. column_constraint (optional):Any constraint (e.g., NOT NULL, DEFAULT, etc.) applied to the new colum...
SQL> select CONSTRAINT_NAME C_NAME,INDEX_NAME,CONSTRAINT_TYPE from user_constraints where TABLE_NAME='EMP' and CONSTRAINT_TYPE='P'; C_NAME INDEX_NAME CONST --- --- --- PK_EMP PK_EMP P query to find unique constraints on a table in oracle SQL> CREATE...
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 ...