- What will happen if you use Delete command without the where clause?
- Can a table have 2 primary keys?
- How can reset primary key ID after delete the row?
- Can you set more than one key as primary key?
- How delete a row in SQL?
- Can a table have two unique keys?
- What is the difference between primary key and unique key?
- How can get last identity value in SQL Server?
- How do you make an identity column start from 1?
- Can we reset identity column in SQL Server?
- How do I reseed a primary key in SQL Server?
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..
Can a table have 2 primary keys?
The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).
How can reset primary key ID after delete the row?
Reset the auto increment field ALTER TABLE `table` AUTO_INCREMENT = number; Replacing ‘number’ with the result of the previous command plus one and replacing table with the table name. If you deleted all the rows in the table, then you could run the alter table command and reset it to 0.
Can you set more than one key as primary key?
A table can have only one primary key, which may consist of single or multiple fields. When multiple fields are used as a primary key, they are called a composite key. If a table has a primary key defined on any field(s), then you cannot have two records having the same value of that field(s).
How delete a row in SQL?
SQL DELETEFirst, you specify the table name where you want to remove data in the DELETE FROM clause.Second, you put a condition in the WHERE clause to specify which rows to remove. If you omit the WHERE clause, the statement will remove all rows in the table.
Can a table have two unique keys?
You can only have one primary key per table, but multiple unique keys. Similarly, a primary key column doesn’t accept null values, while unique key columns can contain one null value each. And finally, the primary key column has a unique clustered index while a unique key column has a unique non-clustered index.
What is the difference between primary key and unique key?
Primary Key is a column that is used to uniquely identify each tuple of the table. It is used to add integrity constraints to the table. Only one primary key is allowed to be used in a table. … Unique key is a constraint that is used to uniquely identify a tuple in a table.
How can get last identity value in SQL Server?
We use SCOPE_IDENTITY() function to return the last IDENTITY value in a table under the current scope. A scope can be a module, trigger, function or a stored procedure.
How do you make an identity column start from 1?
Here is the sample demonstration for resetting identity column values in SQL Server.Create a table. CREATE TABLE dbo.Emp. ( ID INT IDENTITY(1,1), Name VARCHAR(10) )Reset the identity column value. DELETE FROM EMP WHERE ID=3. DBCC CHECKIDENT (‘Emp’, RESEED, 1) INSERT INTO dbo.Emp(Name) VALUES (‘Kalluri’)More items…•
Can we reset identity column in SQL Server?
If you are using an identity column on your SQL Server tables, you can set the next insert value to whatever value you want.
How do I reseed a primary key in SQL Server?
Reset Auto-generated Primary Key(RESEED) at MS SQL ServerDelete all the data from the table.Run below command. reset primary key. Transact-SQL. DBCC CHECKIDENT (‘YourTableName’, RESEED, 1) DBCC CHECKIDENT (‘YourTableName’, RESEED, 1) you can also check the current SEED of your table by below command. check seed. DBCC CHECKIDENT (‘YourTableName’, RESEED, 0);