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Several methods of SQL Optimization

1. To optimize the query, full table scanning should be avoided as far as possible.

2. The null value judgment of the field in the where clause should be avoided as far as possible.

3. Try to avoid using the! = or operator in the where clause.

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

Why optimize SQL

At the initial stage of the launch of our development project, due to the relatively small amount of business data, the impact of the execution efficiency of some SQL on the running efficiency of the program is not obvious, and the developers and operators are unable to judge the running efficiency of the program by SQL, so there is little special optimization for SQL, but with the accumulation of time and the increase of the amount of business data, the influence of the execution efficiency of SQL on the running efficiency of the program increases gradually. At this point, 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 the user to specify the data storage method, nor does it require the user to know 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 have great flexibility and powerful functions.

These are the details of several methods of SQL optimization, please pay more attention to other related articles!

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