MySQL syntax SQL command parsing

MySQL is a commonly used relational database management system that uses SQL (Structured Query Language) as the language for operating databases.

1. Database operation

1. create database_namedatabase

CREATE DATABASE database_name;

2. delete database_namedatabase

DROP DATABASE database_name;

3. Select the database to use

USE database_name;

2. Table operation

1. Create table_namea table with specified columns and constraints

CREATE TABLE table_name (
  column1 datatype constraint,
  column2 datatype constraint,
  ...
);

2. delete table_nametable

DROP TABLE table_name;

3. Add a column to table_namea table, modify a column definition, or delete a column

ALTER TABLE table_name
  ADD column_name datatype constraint,
  MODIFY column_name datatype constraint,
  DROP column_name;

3. Data operation

1. insert data

INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);

2. Query data

SELECT column1, column2, ...
FROM table_name
WHERE condition;

3. update data

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

4. delete data

DELETE FROM table_name
WHERE condition;

4. Data filtering and sorting

1. Conditional filtering: use WHEREkeywords to conditionally filter the query results

SELECT column1, column2, ...
FROM table_name
WHERE condition;

2. Sorting: ORDER BYSort query results using keywords

SELECT column1, column2, ...
FROM table_name
ORDER BY column1 ASC, column2 DESC;

5. Data Aggregation and Grouping

1. Aggregate Functions: Use aggregate functions to calculate the total, sum, average, maximum, and minimum of a column

SELECT COUNT(column), SUM(column), AVG(column), MAX(column), MIN(column)
FROM table_name;

2. Grouping: column1group by column and use aggregate functions to calculate the values ​​of other columns

SELECT column1, aggregate_function(column2)
FROM table_name
GROUP BY column1;

6. Connection operation

1. Inner join: perform an inner join based on the columns of two tables

SELECT column1, column2, ...
FROM table1
INNER JOIN table2
ON table1.column = table2.column;

2. Outer join: left join based on the columns of two tables

SELECT column1, column2, ...
FROM table1
LEFT JOIN table2
ON table1.column = table

2.column;

7. Indexing and optimization

1. Create Index: Create an index on the columns of the table to improve query performance

CREATE INDEX index_name
ON table_name (column1, column2, ...);

2. Query optimization: Use EXPLAINkeywords to analyze query statements to understand query execution plans and performance optimization suggestions

EXPLAIN SELECT column1, column2, ...
FROM table_name
WHERE condition;