From 316e721ac955722e5d66d4905cd7f916c5f40297 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9B=B9=E5=BD=AC=E5=BD=AC?= <3204487492@qq.com>
Date: Thu, 2 Sep 2021 09:41:26 +0000
Subject: [PATCH] zy

---
 "\346\233\271\345\275\254\345\275\254.sql" | 64 ++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 "\346\233\271\345\275\254\345\275\254.sql"

diff --git "a/\346\233\271\345\275\254\345\275\254.sql" "b/\346\233\271\345\275\254\345\275\254.sql"
new file mode 100644
index 0000000..caad050
--- /dev/null
+++ "b/\346\233\271\345\275\254\345\275\254.sql"
@@ -0,0 +1,64 @@
+create database class;
+use class;
+
+select LENGTH('123ab中国c'),OCTET_LENGTH('123ab中国c')--字符长度
+
+select CHAR_LENGTH('123ab中国c')--字节长度
+
+
+select REPLACE('123456789','2','999')--把2替换成999
+select INSERT('123456789',2,3,'999')--把从2开始的3为数的替换成999
+
+
+select LEFT('123456789',3)--从左边截取3位数
+select RIGHT('123456789',3)--从右边截取3位数
+select SUBSTRING('123456789',-4,3)--从右边第5位截取3位数
+
+select CONCAT('abc','123','中国')--拼接
+
+select REVERSE('123456789')--逆序
+
+select UPPER('中国abcEFG123')--小写转大写
+select LOWER('中国abcEFG123')--大写转小写
+
+select TRIM('    12  3  ');--去掉左边的空格
+select RTRIM('   12  3  ');--去掉右边的空格
+select REPLACE('       12  3    ',' ','');--去掉所有的空格
+
+
+select NOW()--获取当前时间日期
+
+SELECT UNIX_TIMESTAMP('2021-09-02 15:13:28');--转化秒
+SELECT FROM_UNIXTIME(1630566808);--转化日期
+
+
+select *,if(money>=0,'正常','异常')资金状态 from user;
+
+select *,(
+CASE 
+	WHEN money>=0 THEN
+		'正常'
+	ELSE
+		'异常'
+END 
+
+)资金状态
+from user;
+
+
+select *,(
+CASE status
+	WHEN 1 THEN
+		'在线'
+		WHEN 2 THEN
+		'限制登入'
+		WHEN 4 THEN
+	'被删除'
+	ELSE
+		'未知状态'
+END 
+)用户状态
+ from user;
+
+
+SELECT *, IFNULL(IDCODE,0)IDCODE from user;
\ No newline at end of file
-- 
Gitee