Help Center/ GaussDB(DWS)/ FAQs/ Database Usage/ How Can I Delete Table Data Efficiently?
Updated on 2023-11-21 GMT+08:00
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How Can I Delete Table Data Efficiently?

Yes. TRUNCATE is more efficient than DELETE for deleting massive data.

For details, see TRUNCATE.

Function

TRUNCATE quickly removes all rows from a database table.

It has the same effect as the unconditional DELETE, but TRUNCATE is faster, especially for large tables, because it does not scan tables.

Functions

  • TRUNCATE TABLE works like a DELETE statement with no WHERE clause, that is, emptying a table.
  • TRUNCATE TABLE uses less system and transaction log resources.
    • DELETE deletes a row each time, and records each deletion in the transaction log.
    • TRUNCATE TABLE deletes all rows in a table by releasing the data page, and only records each releasing of the data page in the transaction log.
  • TRUNCATE, DELETE, and DROP are different in that:
    • TRUNCATE TABLE deletes content, releases space, but does not delete definitions.
    • DELETE TABLE deletes content, but does not delete definitions or release space.
    • DROP TABLE deletes content and definitions, and releases space.

Examples

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--Create a table.CREATE TABLE tpcds.reason_t1 AS TABLE tpcds.reason;

--Truncate the table.TRUNCATE TABLE tpcds.reason_t1;

--Drop the table.DROP TABLE tpcds.reason_t1;

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--Create a partitioned table.
CREATE TABLE tpcds.reason_p
(
  r_reason_sk integer,
  r_reason_id character(16),
  r_reason_desc character(100)
)PARTITION BY RANGE (r_reason_sk)
(
  partition p_05_before values less than (05),
  partition p_15 values less than (15),
  partition p_25 values less than (25),
  partition p_35 values less than (35),
  partition p_45_after values less than (MAXVALUE)
);

--Insert data.
INSERT INTO tpcds.reason_p SELECT * FROM tpcds.reason;

--Truncate the p_05_before partition.
ALTER TABLE tpcds.reason_p TRUNCATE PARTITION p_05_before;

--Truncate the p_15 partition.
ALTER TABLE tpcds.reason_p TRUNCATE PARTITION for (13);

--Truncate the partitioned table.
TRUNCATE TABLE tpcds.reason_p;

-- Delete the table:
DROP TABLE tpcds.reason_p;

Parent topic: Database Usage