DELETE
queries help remove unnecessary or incorrect data from your database. This short guide outlines their structure and practical usage.
The basic form of a DELETE
query looks like this:
DELETE FROM table_name
WHERE condition;
Some helpful options include these four alternatives.
LOW_PRIORITY: Executes the query with lower priority.
QUICK: Optimizes how indexes are handled during deletion.
IGNORE: Ignores errors and continues deleting.
LIMIT: Deletes a specified number of rows.
Working with Partitions
For partitioned tables, DELETE
queries can remove data from specific sections:
DELETE FROM table_name PARTITION (partition_name)
WHERE condition;
Alternatively, using TRUNCATE
can speed up deletion:
TRUNCATE table_name PARTITION (partition_name);
FAQ
What distinguishes DELETE from TRUNCATE?
DELETE
selectively removes rows; TRUNCATE
clears the whole table or partition. TRUNCATE
is faster and has less overhead.
Can DELETE queries be made faster?
Yes, eliminating unnecessary indexes can improve performance.
When should DELETE be used over TRUNCATE?
DELETE
should be used for specific data removal, while TRUNCATE
is ideal for clearing all data.
What role does WHERE play in DELETE queries?
WHERE
specifies which rows to delete, ensuring precision.
Summary
DELETE
queries are fundamental in maintaining database efficiency. Knowing when to use them and understanding their variations, like TRUNCATE
, can significantly optimize performance. For further reading and detailed examples, visit the original article DELETE Queries – Advanced CRUD explanation part 4.
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