Several methods of SQL optimization

Several methods of SQL optimization

1. To optimize the query, full table scans should be avoided as much as possible;

2. Try to avoid making null value judgments on fields in the where clause;

3. Try to avoid using the != or <> operators in the where clause;

4. "in" and "not in" should also be used with caution, otherwise it will lead to a full table scan.

Why should we optimize SQL

In the early days of our development project, due to the relatively small amount of business data, some SQL The impact of execution efficiency on program running efficiency is not obvious, and development and operation and maintenance personnel cannot judge how efficient SQL is on program running. Therefore, special optimization of SQL is rarely carried out. Over time, the amount of business data increases. With the increase of SQL execution efficiency, the impact of SQL execution efficiency on the running efficiency of the program is gradually increasing. At this time, it is necessary to optimize SQL.

What is SQL

Structured Query Language (Structured Query Language), referred to as SQL, is a special-purpose programming language , is a database query and programming language used to access data and query, update and manage relational database systems.

Structured Query Language is a high-level, non-procedural programming language that allows users to work on high-level data structures. It does not require users to specify the data storage method, nor does it require users to understand the specific data storage method, so different database systems with completely different underlying structures can use the same structured query language as the interface for data input and management. Structured Query Language statements can be nested, which makes it extremely flexible and powerful.

Recommended tutorial: "MySQL Tutorial"

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