SUBSTR对SQL查询

Question

这个查询：

SELECT substr(d.title,0,7) 
FROM orders_total d, orders o 
WHERE d.orders_id = o.orders_id 

给了我这个错误：

#1064 - You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near '(d . title , '0' , '7') from orders_total d , orders o

它的工作原理没有SUBSTR，但我不能让它使用它。

Answer 1

从mySql documentation：

For all forms of SUBSTRING(), the position of the first character in the string from which the substring is to be extracted is reckoned as 1.

所以，你必须改变0 1：

SELECT substr(d.title,1,7) 
FROM orders_total d, orders o 
WHERE d.orders_id = o.orders_id 

Answer 2

SELECT LEFT(d.title,7) FROM orders_total d, orders o WHERE d.orders_id = o.orders_id 

Answer 3

sbustr应子串，并开始对指数1，而不是0

据我所知，