MySQL: TRUNCATE TABLE Statement
- Description. The TRUNCATE TABLE statement is used to remove all records from a table in MySQL. ...
- Syntax. If specified, it is the name of the database. ...
- Note. When you truncate a table, the AUTO_INCREMENT counters on the table will be reset. ...
- Example. ...
Why truncate is faster than delete?
The TRUNCATE TABLE statement is faster and more efficient than the DELETE statement in SQL databases. This is because TRUNCATE TABLE is a DDL command, unlike DELETE it does not delete records one by one and logs them to the log table, but drops the whole table and recreates the structure. This is why we cannot use the WHERE clause with the TRUNCATE TABLE command.
Why is truncate faster than delete in SQL Server?
There is a lot going on there, but the basic logic is this:
- Pull the test-specific data (TestID and all the parameters) from the dbo.Tests table
- Give SQL Server a kick by making an sp_configure change and clearing buffers and plan cache
- Restore a clean copy of AdventureWorks, with all 10 million rows intact, and no indexes
- Change the options of the database depending on the parameters for the current test
How to restore your MySQL database?
- A Linux operating system
- MySQL installed
- An existing database
- Mysqldump utility (should be included with your MySQL software)
Why truncate is a DDL command?
- TRUNCATE is a DDL command
- TRUNCATE is executed using a table lock and the whole table is locked to remove all records.
- We cannot use Where clause with TRUNCATE.
- TRUNCATE removes all rows from a table.
- Minimal logging in a transaction log, so it is performance wise faster.
What is the purpose of TRUNCATE command?
TRUNCATE TABLE removes all rows from a table, but the table structure and its columns, constraints, indexes, and so on remain. To remove the table definition in addition to its data, use the DROP TABLE statement.
What happens when you TRUNCATE a table MySQL?
The TRUNCATE statement in MySQL removes the complete data without removing its structure. It is a part of DDL or data definition language command. Generally, we use this command when we want to delete an entire data from a table without removing the table structure.
Why is TRUNCATE used in SQL?
In SQL, the TRUNCATE TABLE statement is a Data Definition Language (DDL) operation that marks the extents of a table for deallocation (empty for reuse). The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms.
What is difference between delete and TRUNCATE in MySQL?
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. On the other hand , delete statement can be used for deleting the specific data.
What is the difference between deleting all records from a table and truncating the table?
The DELETE statement removes rows one at a time and records an entry in the transaction log for each deleted row. TRUNCATE TABLE removes the data by deallocating the data pages used to store the table data and records only the page deallocations in the transaction log. DELETE command is slower than TRUNCATE command.
What is difference between truncate and DROP TABLE?
In SQL, the DROP command is used to remove the whole database or table indexes, data, and more. Whereas the TRUNCATE command is used to remove all the rows from the table.
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 .
Does truncating a table reset the identity?
TRUNCATE resets the identity value to the original seed value of the table.
Why TRUNCATE is faster than DROP?
TRUNCATE is a DDL(Data Definition Language) command. It is used to delete all the tuples from the table. Like the DROP command, the TRUNCATE command also does not contain a WHERE clause. The TRUNCATE command is faster than both the DROP and the DELETE command.
Which is better delete or TRUNCATE?
TRUNCATE command is faster than the DELETE command as it deallocates the data pages instead of rows and records data pages instead of rows in transaction logs. Once the record deletes by using the TRUNCATE command, we cannot recover it back.
Can we rollback the data after 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.
Does TRUNCATE free space?
Truncating a table does not give any free space back to the disk - you need to run a SHRINKDATABASE operation for the allocated space to be successfully de-allocated and returned to the disk.
What is a TRUNCATE TABLE statement?
Logically, the TRUNCATE TABLE statement is like a DELETE statement without a WHERE clause that deletes all rows from a table, or a sequence of DROP TABLE and CREATE TABLE statements.
Does truncate table trigger delete?
The TRUNCATE TABLE statement does not fire DELETE triggers associated with the table that is being truncated. Unlike a DELETE statement, the number of rows affected by the TRUNCATE TABLE statement is 0, which should be interpreted as no information.
Example 1
Following is an example of the TRUNCATE () function. In here, we are limiting the number of digits after the decimal to 3.
Example 4
If the value of the parameter D (value chosen for the number digits) is 0, all the digits after the decimal will be removed −
Example 5
If you pass a negative value for the second parameter (D), all the decimal places are removed from the given number and in addition, the specified number of digits from the given number (left to the decimal point) will be modified as zeros.
Example 6
You can use TRUNCATE function to remove digits after the decimal from the values in a column. Assume we have created a table named employee_tbl in MySQL using the following quires −
What is truncating a table in MySQL?
In MySQL, truncating a table is a fast way to clear out records from a table if you don't need to worry about rolling back. In most cases, MySQL handles the process of table truncation a bit differently than other databases such as Oracle or SQL Server. Let's look at an example of how to use the TRUNCATE TABLE statement in MySQL.
How does MySQL truncate tables?
MySQL truncates the table by dropping and creating the table. Thus, the DELETE triggers for the table do not fire during the truncation. Starting in MySQL 5.5, you can not truncate an InnoDB table that is referenced by a foreign key in another table.
What is truncate table?
The TRUNCATE TABLE statement is used to remove all records from a table in MySQL. It performs the same function as a DELETE statement without a WHERE clause. Warning: If you truncate a table, the TRUNCATE TABLE statement can not be rolled back.
Description
The MySQL TRUNCATE function returns a number truncated to a certain number of decimal places.
Example
Let's look at some MySQL TRUNCATE function examples and explore how to use the TRUNCATE function in MySQL.
What does a TRUNCATE statement do?
What Does the SQL TRUNCATE TABLE Statement Do? The SQL TRUNCATE statement, or TRUNCATE TABLE statement, removes all data from a table. It’s similar to the DELETE statement without a WHERE clause.
Why is there no where clause in SQL?
This is because all of the data in the table is removed when you run a TRUNCATE statement. With the DELETE statement, you can delete all records, or use the WHERE clause to delete some records.
TRUNCATE Function – Truncating a Number to a Certain Number of Decimal Places
First, the TRUNCATE function. The TRUNCATE function reduces the number of decimal places for a given number.
TRUNCATE Statement – Deleting ALL Data from a Table Irreversibly
The TRUNCATE statement is an entirely different thing. It irreversibly deletes ALL data from a given table.
