前言：
遇到朋友提问，如下：
SELECT * FROM ali_users WHERE DATEDIFF(CAST(CONCAT(DATE_FORMAT(NOW(),'%y'),DATE_FORMAT(birthday,'-%m-%d'))AS DATE),CAST(DATE_FORMAT(NOW(),'%y-%m-%d') AS DATE)) <=1
1，准备测试数据，需要包含跨年的数据
1.1，准备测试数据的SQL
USE test;
DROP TABLE IF EXISTS ali_users;
CREATE TABLE ali_users (username VARCHAR(10),birthday DATE NOT NULL,iphone VARCHAR(16));
INSERT INTO ali_users SELECT \'MaoYi\',\'1985-09-04\',\'13998786543\' UNION ALL
SELECT \'LiuEr\',\'1985-08-30\',\'13998786543\' UNION ALL
SELECT \'ZhangSan\',\'1981-01-01\',\'13998786543\' UNION ALL
SELECT \'LiSi\',\'1983-01-02\',\'13998786543\' UNION ALL
SELECT \'WangWu\',\'1984-11-01\',\'13998786543\' UNION ALL
SELECT \'ZhaoLiu\',\'1984-11-01\',\'13998786543\' UNION ALL
SELECT \'SongQi\',\'1986-08-31\',\'13998786543\' UNION ALL
SELECT \'HuangBa\',\'1989-09-01\',\'13998786543\' UNION ALL
SELECT \'ZengJiu\',\'1989-09-02\',\'13998786543\' UNION ALL
SELECT \'LuoShi\',\'1985-09-03\',\'13998786543\' UNION ALL
SELECT \'Tom\',\'1995-09-05\',\'13998786543\' UNION ALL
SELECT \'Licy\',\'1991-12-30\',\'13998286543\' UNION ALL
SELECT \'Cari\',\'1992-12-31\',\'13998286543\' UNION ALL
SELECT \'Mark\',\'1992-01-03\',\'13998286543\' UNION ALL
SELECT \'Ruby\',\'1992-01-04\',\'13998286547\';
1.2，在
数据库命令行执行SQL
mysql> USE test;
DATABASE CHANGED
mysql> DROP TABLE IF EXISTS ali_users;
QUERY OK, 0 ROWS affected (0.00 sec)
mysql> CREATE TABLE ali_users (username VARCHAR(10),birthday DATE NOT NULL,iphone VARCHAR(16));
QUERY OK, 0 ROWS affected (0.01 sec)
mysql> INSERT INTO ali_users SELECT \'MaoYi\',\'1985-09-04\',\'13998786543\' UNION ALL
-> SELECT \'LiuEr\',\'1985-08-30\',\'13998786543\' UNION ALL
-> SELECT \'ZhangSan\',\'1981-01-01\',\'13998786543\' UNION ALL
-> SELECT \'LiSi\',\'1983-01-02\',\'13998786543\' UNION ALL
-> SELECT \'WangWu\',\'1984-11-01\',\'13998786543\' UNION ALL
-> SELECT \'ZhaoLiu\',\'1984-11-01\',\'13998786543\' UNION ALL
-> SELECT \'SongQi\',\'1986-08-31\',\'13998786543\' UNION ALL
-> SELECT \'HuangBa\',\'1989-09-01\',\'13998786543\' UNION ALL
-> SELECT \'ZengJiu\',\'1989-09-02\',\'13998786543\' UNION ALL
-> SELECT \'LuoShi\',\'1985-09-03\',\'13998786543\' UNION ALL
-> SELECT \'Tom\',\'1995-09-05\',\'13998786543\' UNION ALL
-> SELECT \'Licy\',\'1991-12-30\',\'13998286543\' UNION ALL
-> SELECT \'Cari\',\'1992-12-31\',\'13998286543\' UNION ALL
-> SELECT \'Mark\',\'1992-01-03\',\'13998286543\' UNION ALL
-> SELECT \'Ruby\',\'1992-01-04\',\'13998286547\';
QUERY OK, 15 ROWS affected (0.01 sec)
Records: 15 Duplicates: 0 WARNINGS: 0
mysql> SELECT * FROM ali_users;
+----------+------------+-------------+
| username | birthday | iphone |
+----------+------------+-------------+
| MaoYi | 1985-09-04 | 13998786543 |
| LiuEr | 1985-08-30 | 13998786543 |
| ZhangSan | 1981-01-01 | 13998786543 |
| LiSi | 1983-01-02 | 13998786543 |
| WangWu | 1984-11-01 | 13998786543 |
| ZhaoLiu | 1984-11-01 | 13998786543 |
| SongQi | 1986-08-31 | 13998786543 |
| HuangBa | 1989-09-01 | 13998786543 |
| ZengJiu | 1989-09-02 | 13998786543 |
| LuoShi | 1985-09-03 | 13998786543 |
| Tom | 1995-09-05 | 13998786543 |
| Licy | 1991-12-30 | 13998286543 |
| Cari | 1992-12-31 | 13998286543 |
| Mark | 1992-01-03 | 13998286543 |
| Ruby | 1992-01-04 | 13998286547 |
+----------+------------+-------------+
15 ROWS IN SET |