'=' 和有什么区别？不使用通配符时的运算符和 LIKE
我做这个问题是因为我找不到具有相同原因的问题。原因是当我使用 LIKE 时，我得到一致的结果，而当我使用 (=) 运算符时，我得到不一致的结果。
案例
我有一个大视图（viewX），具有多个内部联接和左联接，其中某些列具有空值，因为数据库定义允许这样做。
- 当我打开此视图时，我看到例如：结果为 8 行。
- 例如，当我运行：
select * from viewX where column_int = 34 and type_string = 'xyz'时，此查询向我显示 100 行，这些行未在视图结果中定义。 [不一致]
但是
- 当我运行
select * from viewX where column_int = 34 and type_string like 'xyz'时，此查询仅显示 4 行，这是我打开时在视图中定义的（请参阅 1. ）[一致]
有人知道这里发生了什么吗？
I do this question, because I can't found a question with the same reason. The reason is when I use LIKE, I get CONSISTENT RESULTS, and when I use (=) operator I get INCONSISTENT RESULTS.
THE CASE
I have a BIG VIEW (viewX) with multiple inner joins and left joins, where some columns have null values, because the database definition allows for that.
- When I open this VIEW I see for example: 8 rows as result.
- When I run for example:
select * from viewX where column_int = 34 and type_string = 'xyz', this query shows me 100 rows, that aren't defined in the result of the view. [INCONSISTENT]
BUT
- When I run
select * from viewX where column_int = 34 and type_string like 'xyz', this query show me only 4 rows, that is defined in the view when I opened (see 1.) [CONSISTENT]
Does anyone idea, of what is happening here?
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从文档中......
“根据 SQL 标准，LIKE 在每个字符的基础上执行匹配，因此它可以产生与 = 比较运算符不同的结果：”
更重要的是（使用 LIKE 时）：
“字符串比较不区分大小写，除非操作数之一是二进制字符串'，
来自：
http://dev.mysql.com/doc/refman /5.0/en/string-comparison-functions.html
From the documentation.....
'Per the SQL standard, LIKE performs matching on a per-character basis, thus it can produce results different from the = comparison operator: '
more importantly (when using LIKE):
'string comparisons are not case sensitive unless one of the operands is a binary string'
from :
http://dev.mysql.com/doc/refman/5.0/en/string-comparison-functions.html
根据 MySQL 文档
LIKE的功能与=不同，尤其是当尾随或前导空格时。您需要发布您的实际查询，但我猜它与已知的差异有关。
Per the MySQL documentation
LIKEdoes function differently than=, especially when you have trailing or leading spaces.You need to post your actual query but I'm guessing it's related to the known variances.