Question

我有一张这样的桌子：

mysql> select * from users;
+--------+----------+------------+-----------+
| userid | username | password   | privilege |
+--------+----------+------------+-----------+
|      1 | user1    | password   |         1 |
|      2 | david    | goodboy    |         1 |
|      3 | admin    | mastermold |         5 |
|      4 | user4    | password4  |         1 |
|      5 | user5    | password5  |         2 |
|      6 | user6    | password6  |         1 |
|      7 | user7    | password7  |         1 |
+--------+----------+------------+-----------+
7 rows in set

现在，如何通过唯一的选择查询提取名为“david”的用户名密码而不存储“密码”，结果在一个字段中。（不接受“select * from users”）？

Answer 1

尝试

select password from users where username='david';

Answer 2

嗯，你的意思是你的查询结果不应该有字符串“password”，如果我已经正确使用它。即使我发布了答案，你应该考虑@MarcB评论并尝试首先学习SQL。

您的查询应该是这样的

select `password` from users where username='david' 
and lower(`password`) not like '%password%';

Answer 3

没有提到“密码”？好吧，你可以将列名称抓取到一个变量中，然后像sqlFiddle

那样使用它

SET @columnName = (SELECT COLUMN_NAME FROM
                   INFORMATION_SCHEMA.COLUMNS
                   WHERE TABLE_NAME = 'users' 
                   AND ORDINAL_POSITION = 3);
SET @sql = CONCAT("SELECT ",@columnName," FROM users WHERE username = 'david'");
prepare statement FROM @sql;
execute statement;

MYSQL。使用列筛选提取数据

3 个答案: