MySQL查询 - 使用ORDER BY rand强制区分大小写（）

Question

Is it possible to force case-sensitive for a query?

Mine sounds like this:

"SELECT g_path FROM glyphs WHERE g_glyph = :g_glyph ORDER BY rand()"

if g_glyph = r, the result can be R or r and it's not what I expect. I'm looking for a case-sensitive return.

I googled my issue and I found this solution:

/*Case-sensitive sort in descending order.
In this query, ProductName is sorted in 
case-sensitive descending order.
*/
SELECT ProductID, ProductName, UnitsInStock
FROM products
ORDER BY BINARY ProductName DESC;

But the following line doesn't work at all:

"SELECT g_path FROM glyphs WHERE g_glyph = :g_glyph ORDER BY BINARY rand()"

Any Suggestion?

Thank you very much for your help.

Answer 1

The order and equality of characters is defined by the collation . In most cases, a case-insensitive collation is used.

If you need to use a strict, case-sensitive comparison for a specific datum, use the BINARY operator :

mysql> SELECT 'a' = 'A';
        -> 1
mysql> SELECT BINARY 'a' = 'A';
        -> 0
mysql> SELECT 'a' = 'a ';
        -> 1
mysql> SELECT BINARY 'a' = 'a ';
        -> 0

So in your case:

SELECT g_path FROM glyphs WHERE BINARY g_glyph = :g_glyph ORDER BY rand()

Answer 2

This is covered in the manual page Case Sensitivity in String Searches .

You need to specify a case sensitive or binary collation.

The default character set and collation are latin1 and latin1_swedish_ci, so nonbinary string comparisons are case insensitive by default. This means that if you search with col_name LIKE 'a%', you get all column values that start with A or a. To make this search case sensitive, make sure that one of the operands has a case sensitive or binary collation. For example, if you are comparing a column and a string that both have the latin1 character set, you can use the COLLATE operator to cause either operand to have the latin1_general_cs or latin1_bin collation:

 col_name COLLATE latin1_general_cs LIKE 'a%' col_name LIKE 'a%' COLLATE latin1_general_cs col_name COLLATE latin1_bin LIKE 'a%' col_name LIKE 'a%' COLLATE latin1_bin 

If you want a column always to be treated in case-sensitive fashion, declare it with a case sensitive or binary collation. See Section 13.1.14, “CREATE TABLE Syntax”.

The _cs in the collation name stands for "case sensitive".