What is MySQL optimize?
OPTIMIZE TABLE reorganizes the physical storage of table data and associated index data, to reduce storage space and improve I/O efficiency when accessing the table. After doing substantial insert, update, or delete operations on columns that are part of a FULLTEXT index in an InnoDB table.
How do you optimize a SQL query?
Supercharge Your SQL Queries for Production Databases
- Define business requirements first.
- SELECT fields instead of using SELECT *
- Avoid SELECT DISTINCT.
- Create joins with INNER JOIN (not WHERE)
- Use WHERE instead of HAVING to define filters.
- Use wildcards at the end of a phrase only.
- Use LIMIT to sample query results.
How does MySQL optimize queries?
Optimize Queries With MySQL Query Optimization Guidelines
- Avoid using functions in predicates.
- Avoid using a wildcard (%) at the beginning of a predicate.
- Avoid unnecessary columns in SELECT clause.
- Use inner join, instead of outer join if possible.
- Use DISTINCT and UNION only if it is necessary.
How does explain work in the MySQL optimizer?
EXPLAIN works with SELECT, DELETE, INSERT, REPLACE, and UPDATE statements. When EXPLAIN is used with an explainable statement, MySQL displays information from the optimizer about the statement execution plan. That is, MySQL explains how it would process the statement, including information about how tables are joined and in which order.
How to optimize a select.where query?
The main considerations for optimizing queries are: To make a slow SELECT WHERE query faster, the first thing to check is whether you can add an index. Set up indexes on columns used in the WHERE clause, to speed up evaluation, filtering, and the final retrieval of results.
What do select statements do in a database?
Queries, in the form of SELECT statements, perform all the lookup operations in the database. Tuning these statements is a top priority, whether to achieve sub-second response times for dynamic web pages, or to chop hours off the time to generate huge overnight reports.
How is the explain statement used in MySQL?
You can use the EXPLAIN statement to determine which indexes are used for a SELECT. See Section 8.3.1, “How MySQL Uses Indexes” and Section 8.8.1, “Optimizing Queries with EXPLAIN” . Isolate and tune any part of the query, such as a function call, that takes excessive time.