Quick Answer: What Would Happen If You Issued A Delete Statement Without A Where Clause?

Which command could you use to quickly remove all data from the rows in a table without deleting the table itself?

TRUNCATE.

TRUNCATE is a statement that will essentially remove all records from the table, just as if you had used DELETE without a WHERE clause.

This means TRUNCATE will remove all records in your table, but its structure will remain intact..

Is the following statement valid ie is it allowed to update rows in one table?

Is the following statement valid, i.e. is it allowed to update rows in one table, based on a subquery from another table? No, this statement will return an error. The statement will fail because the subqueries are returning data from different rows.

Is truncate faster than 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 .

How can you write not equal to in the where clause?

Use <> to negate the where clause. The above can also be restated, you just need to remember some properties of logical expressions: !(

Will the following statement return one row?

Will the following statement return one row? No, it is illegal. You cannot use more than one multi-row function in a SELECT statement. Yes, it will return the highest salary from each employee.

What is a key difference between truncate and delete?

Delete and truncate both commands can be used to delete data of the table. Delete is a DML command whereas truncate is DDL command. Truncate can be used to delete the entire data of the table without maintaining the integrity of the table.

Which is faster truncate or drop table?

But TRUNCATE TABLE is faster and uses fewer system and transaction log resources than DELETE. … If you want to remove table definition and its data, use the DROP TABLE statement. You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint; instead, use DELETE statement without a WHERE clause.

Why delete can be rollback but truncate not?

If TRUNCATE is written in Query Editor surrounded by TRANSACTION and if session is closed, it can not be rolled back but DELETE can be rolled back. … In case of DELETE, SQL Server removes all the rows from table and records them in Log file in case it is needed to rollback in future. Due to that reason it is slow.

Can we rollback truncate?

You cannot ROLLBACK TRUNCATE Simply, you cannot rollback a transaction if it is already committed but you can do something else to get the data back (or at least some parts of it). When you execute the TRUNCATE statement, your data is still in the MDF file.

What does the distinct keyword do when it is used in a select clause?

The DISTINCT clause is used in a SELECT statement to filter duplicate rows in the result set. It ensures that rows returned are unique for the column or columns specified in the SELECT clause.

How many INSERTs can you have in one transaction?

2. How many INSERTs can you have in one transaction? As many as you can execute before the database does an AUTOSAVE. As many as you want until a different DML statement (UPDATE, DELETE or MERGE) is executed.

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

If you will not provide where clause with delete statement, then whole table data will be deleted. Use this very carefully to avoid any unwanted data loss. Delete From Customer; In the syntax above the deletion happens without any condition and will delete all the records of the table.

How many rows will be deleted from the Employees table with the following statement delete from employees where Last_name King ‘;?

How many rows will be deleted from the employees table with the following statement? All rows with last_name = ‘King’ will be deleted. One will be deleted, as there exists one employee named King.

Why use truncate instead of delete?

TRUNCATE TABLE is faster and uses fewer system resources than DELETE , because DELETE scans the table to generate a count of rows that were affected then delete the rows one by one and records an entry in the database log for each deleted row, while TRUNCATE TABLE just delete all the rows without providing any …

How delete a row in SQL?

To remove one or more rows in a table:First, 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 truncate have where condition?

No, TRUNCATE is all or nothing. You can do a DELETE FROM

WHERE but this loses the speed advantages of TRUNCATE . The short answer is no: MySQL does not allow you to add a WHERE clause to the TRUNCATE statement. Here’s MySQL’s documentation about the TRUNCATE statement.

Does truncate free space?

Using TRUNCATE. … A TRUNCATE statement does not affect any structures associated with the table being truncated (constraints and triggers) or authorizations. A TRUNCATE statement also specifies whether space currently allocated for the table is returned to the containing tablespace after truncation.

Which of the following is a conditional expression used in SQL?

The SQL CASE expression is a generic conditional expression, similar to if/else statements in other languages. CASE clauses can be used wherever an expression is valid. condition is an expression that returns a boolean result. If the result is true then the value of the CASE expression is result .