We can also delete an entiredatabasein SQL if needed. This might be carried out with the help of the DROP DATABASE command in MySQL. With this, all the data stored in all the tables in the concerned database will be deleted permanently. Thus, this command should be cautiously used. It...
Comparing TRUNCATE TABLE, DELETE, and DROP TABLE in SQL What Is the DELETE Statement in SQL? See also: How to Remove a Primary Key in SQL How to remove a unique constraint in SQL? How to Delete a Column in SQL How to Delete a Foreign Key Constraint in SQL How to Delete a Row in...
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...
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 ...
DROP TABLE IF EXISTS table3; Remember to turn on foreign key constraint after it’s done: SET FOREIGN_KEY_CHECKS = 1; 2. Using mysqldump There’s another workaround with mysqldump which is faster and easier. First, disable foreign key check: ...
CONSTRAINT fk_ownerID FOREIGN KEY(ownerID)REFERENCES clubMembers(memberID) ); Copy Note that this example provides a name for the foreign key constraint,fk_ownerID. MySQL will automatically generate a name for any constraint you add, but defining one here will be useful when we need to refere...
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...
CREATETEMPORARYTABLEtmp_user (SELECTid, nameFROMuserGROUPBYname ); # Step2: RemoveallrowsfromoriginaltableDELETEFROMuser; # Step3:AddUniqueconstraintALTERTABLEuserADDUNIQUE(name); # Step4: RemoveallrowsfromoriginaltableINSERTIGNOREINTOuser(SELECT*FROMtmp_user); # Step5: Remove temporarytableDROPTABLEtmp...
Introduction to Oracle DROP VIEW statement To remove a view from the database, you use the following DROP VIEW statement: DROP VIEW schema_name.view_name [CASCADE CONSTRAINT];Code language: SQL (Structured Query Language) (sql) 1) schema_name First, you specify the name of the schema that...
Each set of values in its columns can only appear once. So you can't have duplicates. It also has a not null constraint. And creates a unique index in the background.To create one, add the organization index clause to the table definition:...