区分大小写的字符串出现

Question

我正在使用以下查询拆分列值。它适用于不区分大小写的情况，但我希望它能够区分大小写。

例如，在字符串 'Oil is a product Ingredients are' 中，如果我的搜索关键字是 'ingredients'，它应该 return false 而应该只 return true 如果搜索关键字是 'Ingredients'。 mysql 中是否有允许此操作的函数？

SELECT 
  SUBSTRING_INDEX(description, 'Ingredients', 1),
    if(LOCATE('Ingredients', description)>0, SUBSTRING_INDEX(description, 'Ingredients', -1), '')
FROM `product`

Answer 1

来自 mysql 的 LOCATE 函数的文档：

This function is multibyte safe, and is case-sensitive only if at least one argument is a binary string.

也就是说，您需要 cast/convert 您的参数才能执行 case-sensitive 匹配。

例如：如果你的第一条记录是Oil is a product Ingredients are...，你的第二条记录是Oil is a product ingredients are...那么下面的查询：

SELECT 
  LOCATE('ingredients', description) AS match_both_1,
  LOCATE('Ingredients', description) AS match_both_2,
  LOCATE(CAST('ingredients' AS BINARY), CAST(description AS BINARY)) AS match_second,
  LOCATE(CAST('Ingredients' AS BINARY), CAST(description AS BINARY)) AS match_first
FROM product

会给你预期的结果：

| match_both_1 | match_both_2 | match_second | match_first |
|     18       |     18       |      0       |     18      |
|     18       |     18       |     18       |      0      |

参见DEMO。

区分大小写的字符串出现

Case Sensitive String Occurrence

mysql

case-sensitive