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What is truncate table in SQL?

Remarks – Compared to the DELETE statement, TRUNCATE TABLE has the following advantages:

Less transaction log space is used. 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. Fewer locks are typically used. When the DELETE statement is executed using a row lock, each row in the table is locked for deletion. TRUNCATE TABLE always locks the table (including a schema (SCH-M) lock) and page but not each row. Without exception, zero pages are left in the table. After a DELETE statement is executed, the table can still contain empty pages. For example, empty pages in a heap cannot be deallocated without at least an exclusive (LCK_M_X) table lock. If the delete operation does not use a table lock, the table (heap) will contain many empty pages. For indexes, the delete operation can leave empty pages behind, although these pages will be deallocated quickly by a background cleanup process.

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. If the table contains an identity column, the counter for that column is reset to the seed value defined for the column.

What is truncate vs DELETE in SQL?

DELETE vs TRUNCATE DELETE is a SQL command that removes one or multiple rows from a table using conditions. TRUNCATE is a SQL command that removes all the rows from a table without using any condition. It is a DML(Data Manipulation Language) command.

What is truncate and DELETE?

DELETE vs. TRUNCATE Comparison Chart – The following comparison chart explains their main differences in a quick manner:

Comparison Basis	DELETE	TRUNCATE
Definition	The delete statement is used to remove single or multiple records from an existing table depending on the specified condition.	The truncate command removes the complete data from an existing table but not the table itself. It preserves the table structure or schema.
Language	It is a DML (Data Manipulation Language) command.	It is a DDL (Data Definition Language) command.
WHERE	It can use the WHERE clause to filter any specific row or data from the table.	It does not use the WHERE clause to filter records from the table.
Permission	We need to have DELETE permission to use this command.	We need to have ALTER permission to use this command.
Working	This command eliminates records one by one.	This command deletes the entire data page containing the records.
Lock	It will lock the row before deletion.	It will lock the data page before deletion.
Table Identity	This command does not reset the table identity because it only deletes the data.	It always resets the table identity.
Transaction	It maintains transaction logs for each deleted record.	It does not maintain transaction logs for each deleted data page.
Speed	Its speed is slow because it maintained the log.	Its execution is fast because it deleted entire data at a time without maintaining transaction logs.
Trigger	This command can also activate the trigger applied on the table and causes them to fire.	This command does not activate the triggers applied on the table to fire.
Restore	It allows us to restore the deleted data by using the COMMIT or ROLLBACK statement.	We cannot restore the deleted data after using executing this command.
Indexed view	It can be used with indexed views.	It cannot be used with indexed views.
Space	The DELETE statement occupies more transaction space than truncate because it maintains a log for each deleted row.	The TRUNCATE statement occupies less transaction space because it maintains a transaction log for the entire data page instead of each row.

Is TRUNCATE faster than DELETE?

Difference between DELETE and TRUNCATE – GeeksforGeeks DELETE is a command and is used when we specify the row(tuple) that we want to remove or delete from the table or relation. The DELETE command can contain a WHERE clause. If the WHERE clause is used with the DELETE command then it removes or deletes only those rows(tuple) that satisfy the condition otherwise by default it removes all the tuples(rows) from the table.

1. Remember that DELETE logs the row deletions.
2. Syntax: DELETE command DELETE FROM TableName WHERE condition; TRUNCATE is a command and is used to delete all the rows or tuples from a table.
3. Unlike the DELETE command, the TRUNCATE command does not contain a WHERE clause.
4. In the TRUNCATE command, the transaction log for each deleted data page is not recorded.

Unlike the DELETE command, the TRUNCATE command is fast. We cannot roll back the data after using the TRUNCATE command. Syntax: TRUNCATE command TRUNCATE TABLE TableName; Let us see the difference between DELETE and TRUNCATE commands are as follows:

Delete	Truncate
The DELETE command is used to delete specified rows(one or more).	While this command is used to delete all the rows from a table.
It is a DML(Data Manipulation Language) command.	While it is a DDL(Data Definition Language) command.
There may be a WHERE clause in the DELETE command in order to filter the records.	While there may not be WHERE clause in the TRUNCATE command.
In the DELETE command, a tuple is locked before removing it.	While in this command, the data page is locked before removing the table data.
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.	While the TRUNCATE command is faster than the DELETE command.
To use Delete you need DELETE permission on the table.	To use Truncate on a table we need at least ALTER permission on the table.
The identity of the fewer column retains the identity after using DELETE Statement on the table.	Identity the column is reset to its seed value if the table contains an identity column.
The delete can be used with indexed views.	Truncate cannot be used with indexed views.
This command can also active trigger.	This command does not active trigger.
DELETE statement occupies more transaction spaces than Truncate.	Truncate statement occupies less transaction spaces than DELETE.

ul> Last Updated : 25 Aug, 2022 Like Article Save Article

: Difference between DELETE and TRUNCATE – GeeksforGeeks

What does TRUNCATE () do?

Definition and Usage – The truncate() method resizes the file to the given number of bytes. If the size is not specified, the current position will be used.

Should I use TRUNCATE or DELETE?

TRUNCATE – The DELETE command is used to delete particular records from a table. Definition The TRUNCATE command is used to delete the complete data from the table. It is a DML command. Language Type It is a DDL command The DELETE command acquires the lock on every deleting record; thus, it requires more locks and resources. Locks and Resources The TRUNCATE command requires fewer locks and resources before deleting the data page because it acquires the lock on the data page It works with the WHERE clause. WHERE Clause It does not work with the WHERE clause. DELETE operation operates on data records and executes deletion one-by-one on records in the order of the queries processed Working TRUNCATE operates on data pages and executes deletion of the whole table data at a time. Its speed is slow as it makes operations in rows and records it in transaction logs Speed Its speed is fast as it only records data pages in transaction logs. It records all the deleted data rows in the transaction log. Transaction Log It records only the deleted data pages in the transaction log. You can restore the data using the COMMIT or ROLLBACK command. Rollback You cannot restore the deleted data after executing this command. The DELETE statement deletes the records and does not interfere with the table’s identity. Table Identity The TRUNCATE statement does not delete the table structure but resets the identity of the table It works with an indexed view. Indexed View It does not work with indexed views. It activates the triggers on the table and causes them to fire Triggers It does not activate the triggers applied on the table.

Can we rollback 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.

1. However, it is not visible because SQL Server is treating this as free space ( TRUNCATE is telling SQL Server to deallocate data pages).
2. The only way to get the data back is to somehow read deallocated data pages and convert them into readable data.
3. You must act fast because free space will be overwritten with new data if not already.

If you can stop your SQL Server instance and make a copy of MDF and LDF files that would buy you more time. There are some tools that may do this kind of restore.

Can we rollback after DELETE?

Data can be rolled back with the DELETE command. Data cannot be rolled back with the TRUNCATE command. Data cannot be rolled back with the DROP command since it permanently deletes the table.

How do I TRUNCATE all data in a table?

The TRUNCATE TABLE statement in SQL is a Data Definition Language (DDL) operation that labels a table’s extents for DE allocation (empty for reuse). This procedure removes all data from a table easily, usually bypassing a variety of integrity checking mechanisms.

How do I DELETE data from a table in SQL TRUNCATE?

TRUNCATE TABLE – TRUNCATE TABLE is similar to DELETE, but this operation is a DDL (Data Definition Language) command. It also deletes records from a table without removing table structure, but it doesn’t use the WHERE clause. Here’s the syntax: TRUNCATE TABLE table_name; If you use this command, all rows in this table will be removed.

Can we rollback TRUNCATE or DELETE?

We can rollback a delete query but not so for truncate and drop. When I execute queries then successfully done with rollback in delete, drop & truncate. We can rollback the data in conditions of Delete, Truncate & Drop.

What are 2 differences between DELETE and TRUNCATE?

Difference Between DELETE and TRUNCATE Command in SQL
DELETE	TRUNCATE
When we wish to remove some or all of the records from a table, we use the DELETE statement.	TRUNCATE is a SQL statement that deletes whole rows from a table.
DELETE is a DML command because it just changes the data in the table.	TRUNCATE is a DDL command.

Is TRUNCATE faster than DELETE in SQL?

Conclusion –

The SQL DROP command is a DDL ( Data Definition Language ) command that deletes the defined table with all its table data, associated indexes, constraints, triggers, and permission specifications. The SQL DELETE command is a DML ( Data Manipulation Language ) command that deletes existing records from the table in the database. The SQL TRUNCATE command is a DDL ( Data Definition Language ) command that modifies the data in the database. The TRUNCATE command helps us delete the complete records from an existing table in the database.

Does TRUNCATE free up space?

15.11.5 Reclaiming Disk Space with TRUNCATE TABLE – To reclaim operating system disk space when truncating an InnoDB table, the table must be stored in its own,ibd file. For a table to be stored in its own,ibd file, innodb_file_per_table must enabled when the table is created.

Additionally, there cannot be a foreign key constraint between the table being truncated and other tables, otherwise the TRUNCATE TABLE operation fails. A foreign key constraint between two columns in the same table, however, is permitted. When a table is truncated, it is dropped and re-created in a new,ibd file, and the freed space is returned to the operating system.

This is in contrast to truncating InnoDB tables that are stored within the InnoDB system tablespace (tables created when innodb_file_per_table=OFF ) and tables stored in shared general tablespaces, where only InnoDB can use the freed space after the table is truncated.

Is TRUNCATE permanent?

TRUNCATE removes all rows from a table. The operation cannot be rolled back and no triggers will be fired.

How long does SQL TRUNCATE take?

If there are zero transactions locking the table schema, the TRUNCATE TABLE command will finish near-instantaneously. The most i have waited so far was 0.1 seconds for truncating a 25GB table. In any case, a TRUNCATE TABLE command does not have undesirable side-effects on anything but other maintenance operations. anx anx 9,018 5 gold badges 24 silver badges 48 bronze badges 0

Why use TRUNCATE SQL?

TRUNCATE vs DROP – Unlike TRUNCATE that resets the table structure, DROP command completely frees the tablespace from the memory. They are both Data Definition Language (DDL) operations as they interact with the definitions of database objects; which allows the database to automatically commit once these commands are executed with no chance to roll back.

DROP	TRUNCATE
The DROP command in SQL removes an entire table from a database including its definition, indexes, constraints, data etc.	The TRUNCATE command is used to remove all of the rows from a table, regardless of whether or not any conditions are met and resets the table definition.
It is a DDL(Data Definition Language) command.	It is also a DDL(Data Definition Language) command.
The table space is completely freed from the memory.	The table still exists in the memory.
All the integrity constraints are removed.	The integrity constraints still exist in the table.
Requires ALTER and CONTROL permissions on the table schema and table respectively, to be able to perform this command.	Only requires the ALTER permissions to truncate the table.
DROP command is much slower than TRUNCATE but faster than DELETE.	TRUNCATE command is faster than both DROP and DELETE commands.

Get certified by completing the course : SQL – TRUNCATE TABLE

Why do you TRUNCATE data?

From Wikipedia, the free encyclopedia In SQL, the TRUNCATE TABLE statement is a Data Manipulation Language (DML) operation that deletes all rows of a table without causing a triggered action. The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms.

It was officially introduced in the SQL:2008 standard, as the optional feature F200, “TRUNCATE TABLE statement”. 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.

The TRUNCATE TABLE mytable statement is logically (though not physically) equivalent to the DELETE FROM mytable statement (without a WHERE clause). The following characteristics distinguish TRUNCATE TABLE from DELETE :

In the Oracle Database, TRUNCATE is implicitly preceded and followed by a commit operation. (This may also be the case in MySQL, when using a transactional storage engine.) Typically, TRUNCATE TABLE quickly deletes all records in a table by deallocating the data pages used by the table. This reduces the resource overhead of logging the deletions, as well as the number of locks acquired. Records removed this way cannot be restored in a rollback operation. Two notable exceptions to this rule are the implementations found in PostgreSQL and Microsoft SQL Server, both of which allow TRUNCATE TABLE statements to be committed or rolled back transactionally. It is not possible to specify a WHERE clause in a TRUNCATE TABLE statement. TRUNCATE TABLE cannot be used when a foreign key references the table to be truncated, since TRUNCATE TABLE statements do not fire triggers, This could result in inconsistent data because ON DELETE / ON UPDATE triggers would not fire. In some computer systems, TRUNCATE TABLE resets the count of an Identity column back to the identity’s seed, In Microsoft SQL Server 2000 and beyond in full recovery mode, every change to the database is logged, so TRUNCATE TABLE statements can be used for tables involved in log shipping,

Is TRUNCATE table safe?

Page 11 – TRUNCATE – empty a table or set of tables TRUNCATE name TRUNCATE quickly removes all rows from a set of tables. It has the same effect as an unqualified DELETE on each table, but since it does not actually scan the tables it is faster. Furthermore, it reclaims disk space immediately, rather than requiring a subsequent VACUUM operation.

This is most useful on large tables. name The name (optionally schema-qualified) of a table to be truncated. CASCADE Automatically truncate all tables that have foreign-key references to any of the named tables, or to any tables added to the group due to CASCADE, RESTRICT Refuse to truncate if any of the tables have foreign-key references from tables that are not to be truncated.

This is the default. Only the owner of a table can TRUNCATE it. TRUNCATE cannot be used on a table that has foreign-key references from other tables, unless all such tables are also truncated in the same command. Checking validity in such cases would require table scans, and the whole point is not to do one.

Warning

TRUNCATE is not MVCC-safe (see for general information about MVCC). After truncation, the table will appear empty to all concurrent transactions, even if they are using a snapshot taken before the truncation occurred. This will only be an issue for a transaction that did not access the truncated table before the truncation happened — any transaction that has done so would hold at least an ACCESS SHARE lock, which would block TRUNCATE until that transaction completes. So truncation will not cause any apparent inconsistency in the table contents for successive queries on the same table, but it could cause visible inconsistency between the contents of the truncated table and other tables in the database. TRUNCATE is transaction-safe, however: the truncation will be safely rolled back if the surrounding transaction does not commit.

Truncate the tables bigtable and fattable : TRUNCATE bigtable, fattable; Truncate the table othertable, and cascade to any tables that reference othertable via foreign-key constraints: TRUNCATE othertable CASCADE; There is no TRUNCATE command in the SQL standard.

What is TRUNCATE vs drop vs DELETE table in SQL?

Conclusion –

The SQL DROP command is a DDL ( Data Definition Language ) command that deletes the defined table with all its table data, associated indexes, constraints, triggers, and permission specifications. The SQL DELETE command is a DML ( Data Manipulation Language ) command that deletes existing records from the table in the database. The SQL TRUNCATE command is a DDL ( Data Definition Language ) command that modifies the data in the database. The TRUNCATE command helps us delete the complete records from an existing table in the database.

What is the difference between TRUNCATE and drop?

What is TRUNCATE? – In SQL, the TRUNCATE command is used to remove all the rows from the table. However, the structure of the table and columns remains the same. It is faster than the DROP command.

S.No	DROP	TRUNCATE
1.	It is used to eliminate the whole database from the table.	It is used to eliminate the tuples from the table.
2.	Integrity constraints get removed in the DROP command.	Integrity constraint doesn’t get removed in the Truncate command.
3.	The structure of the table does not exist.	The structure of the table exists.
4.	Here the table is free from memory.	Here, the table is not free from memory.
5.	It is slow as compared to the TRUNCATE command.	It is fast as compared to the DROP command.

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What is TRUNCATE and load table?

Removes all rows from a table but leaves the table intact (including all privileges and constraints on the table). Also deletes the load metadata for the table, which allows the same files to be loaded into the table again after the command completes.

What are the benefits of TRUNCATE?

Use the TRUNCATE command to remove all rows from a table. This has the same effect as the DELETE command, but is much faster than the DELETE command for large tables. You can use TRUNCATE within a transaction or stored procedure to make other related changes to data in one atomic unit.