MYSQL requires Reading Notes, data filtering in chapter 7, mysql required

MYSQL requires Reading Notes, data filtering in chapter 7, mysql required

Mysql Introduction

MySQL is an open-source Relational Database Management System (RDBMS). the MySQL database system uses the most common database management language-Structured Query Language (SQL) for database management.

Calculation order:

Where can contain any number of and or, allowing the combination of the two for complex and advanced filtering. However, SQL will give priority to the AND operator before or. Brackets can be used if you want to prioritize the use of or conditions.

In: Why use the in operator? Its advantages are as follows.

1. When using a long list of valid options, the in operator syntax is clearer and more intuitive.

2. When IN is used, the order of calculation is easier to manage (because fewer operators are used)

3. The IN operator is generally faster than the OR operator.

4. The biggest advantage of IN is that it can contain other SELECT statements so that the WHERE clause can be dynamically created.

IN MySQL, not mysql supports the use of NOT to reverse the IN, BETWEEN, and EXISITS clauses, which is very different from that allowed by most other DBMS to use NOT to reverse the various conditions.

Advantages of using IN. For a simple where clause, using NOT does NOT have any advantages. However, NOT is very useful in complex clauses. For example, when operators are used together. NOT makes it easy to find rows that do NOT match the condition list.

The above section describes the data filtering content in chapter 7 of MYSQL, which is required for reading notes. I hope it will be helpful to you, we are also very grateful for your support for the help House website!