Quick Answer: Does Drop Table Remove Constraints?

Why drop table if exists?

The DROP TABLE SQL statement enables you to delete a table from the database.

If the table did not exist then attempting to DROP it would cause an error to occur.

The DROP TABLE IF EXISTS SQL statement enables a check to see that the table exists prior to attempting the dropping (deletion) of the table..

How do you drop a unique constraint?

Drop Unique Constraint The syntax for dropping a unique constraint in SQL Server is: ALTER TABLE table_name DROP CONSTRAINT constraint_name; table_name. The name of the table to modify.

What happens when you drop a table in SQL?

It completely removes the table structure and associated indexes, statistics, permissions, triggers and constraints. You might have SQL Views and Stored procedures referencing to the SQL table. SQL Server does not remove these stored procedures and views. We need to drop them explicitly.

Does Drop Table remove indexes?

DROP TABLE removes tables from the database. … DROP TABLE always removes any indexes, rules, triggers, and constraints that exist for the target table. However, to drop a table that is referenced by a view or a foreign-key constraint of another table, CASCADE must be specified.

Why use truncate instead of delete?

TRUNCATE is faster than DELETE , as it doesn’t scan every record before removing it. TRUNCATE TABLE locks the whole table to remove data from a table; thus, this command also uses less transaction space than DELETE . Unlike DELETE , TRUNCATE does not return the number of rows deleted from the table.

What command is used to permanently remove a record from a database table?

SQL Truncate CommandSQL Truncate Command. SQL Truncate is a data definition language (DDL) command. It removes all rows in a table.

What does drop table cascade constraints do?

If you specify DROP TABLE orders CASCADE, Advanced Server will drop the orders table and the items table. If you specify DROP TABLE orders CASCADE CONSTRAINTS, Advanced Server will drop the orders table and remove the foreign key specification from the items table, but not drop the items table.

How do you check if a table exists in SQL?

To check if a table exists in SQL Server, you can use the INFORMATION_SCHEMA. TABLES table. You can use this table with an IF THEN clause do determine how your query responds whether or not a table exists.

What are dropped automatically when table dropped?

By default, MS Sql Server also drops indexes when a table is dropped. … MySQL also drops table indexes when tables are dropped.

How do you drop a constraint?

The SQL syntax to remove a constraint from a table is,ALTER TABLE “table_name” DROP [CONSTRAINT|INDEX] “CONSTRAINT_NAME”;ALTER TABLE Customer DROP INDEX Con_First;ALTER TABLE Customer DROP CONSTRAINT Con_First;ALTER TABLE Customer DROP CONSTRAINT Con_First;

Can we drop primary key?

We can remove PRIMARY KEY constraint from a column of an existing table by using DROP keyword along with ALTER TABLE statement.

How can you tell who dropped a table in SQL Server?

Finding out who dropped a table using the transaction logUSE [master]; GO. CREATE DATABASE [FnDbLogTest]; GO. USE [FnDbLogTest]; GO.CREATE TABLE [TestTable] ( [c1] INT IDENTITY, [c2] CHAR (100) DEFAULT ‘a’); GO. CREATE CLUSTERED INDEX [TT_CL] ON [TestTable] ([c1]); GO. INSERT INTO [TestTable] DEFAULT VALUES; GO.SELECT OBJECT_ID (N’TestTable’); GO.DROP TABLE [TestTable]; GO.

When you drop a table all its trigger objects are deleted with it?

Dropping a table invalidates dependent objects and removes object privileges on the table. If you want to re-create the table, then you must regrant object privileges on the table, re-create the indexes, integrity constraints, and triggers for the table, and respecify its storage parameters.

How do I drop a table with constraints?

DROP TABLE schema_name. table_name [CASCADE CONSTRAINTS | PURGE];…In this statement:First, indicate the table and its schema that you want to drop after the DROP TABLE clause. … Second, specify CASCADE CONSTRAINTS clause to remove all referential integrity constraints which refer to primary and unique keys in the table.More items…

Which clause will allow you to delete a constraint?

The MODIFY clause is used with the ALTER TABLE command to add a PRIMARY KEY constraint to an existing table. A constraint can be renamed using the ALTER TABLE command. The ALTER TABLE command can be used to delete an existing constraint.

What happens if we drop a table?

Dropping a table removes the table definition from the data dictionary. All rows of the table are no longer accessible. All indexes and triggers associated with a table are dropped. … All synonyms for a dropped table remain, but return an error when used.

What will happen if you use Delete command without the where clause?

Delete Query in SQL should always be executed with the WHERE clause to avoid unwanted data loss. Delete statement without WHERE clause will delete all the records of the table and without proper rollback mechanism, your data could be lost forever.

How do you drop a table with foreign key constraints in SQL?

State’ — Drop the foreign key constraint by its name ALTER TABLE dbo….Select the tables you want to DROP.Select “Save to new query window”.Click on the Advanced button.Set Script DROP and CREATE to Script DROP.Set Script Foreign Keys to True.Click OK.Click Next -> Next -> Finish.View the script and then Execute.

Is commit required after drop table in Oracle?

CREATE TABLE and DROP TABLE statements do not commit a transaction if the TEMPORARY keyword is used. … SELECT causes an implicit commit before and after the statement is executed when you are creating nontemporary tables. (No commit occurs for CREATE TEMPORARY TABLE … SELECT .)

Do we need to drop table variable in SQL Server?

We do not require dropping the table variable. As mentioned earlier, the scope of the table variable is within the batch. The scope of it lasts at the end of the batch or procedure.

Is commit required for delete statement?

DELETE requires a COMMIT, but TRUNCATE does not.