MySQL是一款廣泛使用的關系型數據庫管理系統，常用于Web應用程序服務。

以下是MySQL中常用的SQL語句：

1.創建數據庫
CREATE DATABASE databasename;
2.選擇數據庫
USE databasename;
3.創建表格
CREATE TABLE tablename (
column1 datatype,
column2 datatype,
column3 datatype,
....
);
4.插入數據
INSERT INTO tablename (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);
5.更新數據
UPDATE tablename
SET column1 = newvalue1, column2 = newvalue2, ...
WHERE column = value;
6.刪除數據
DELETE FROM tablename
WHERE column = value;
7.查詢數據
SELECT * FROM tablename;
8.按條件查詢
SELECT * FROM tablename
WHERE column = value;
9.按多個條件查詢
SELECT * FROM tablename
WHERE column1 = value1 AND column2 = value2;
10.按指定列排序
SELECT * FROM tablename
ORDER BY column1, column2 DESC;
11.限制返回記錄條數
SELECT * FROM tablename
LIMIT 5;
12.跨表連接查詢
SELECT orders.order_id, customers.customer_name
FROM orders
INNER JOIN customers ON orders.customer_id = customers.customer_id;
13.求平均值
SELECT AVG(column) FROM tablename;
14.求總數
SELECT COUNT(*) FROM tablename;
15.求最大值
SELECT MAX(column) FROM tablename;
16.求最小值
SELECT MIN(column) FROM tablename;
17.對查詢結果進行分組查詢
SELECT column, COUNT(*) FROM tablename
GROUP BY column;
18.使用HAVING對分組結果再次篩選
SELECT column, COUNT(*) FROM tablename
GROUP BY column
HAVING COUNT(*) >1;
19.使用子查詢查詢
SELECT column1 FROM tablename WHERE column2 = (SELECT MAX(column2) FROM tablename);
20.使用正則表達式查詢
SELECT * FROM tablename WHERE column REGEXP '^[a-z]+$';