Question

The classic way to query an SQL database case-insensitively from Java is as follows:

String name = ...;  // get the user's input (case is unknown)
String sql = "select * from Person where lower(name) = ?";
Object jdbcBindVariable = name.toLowerCase();
// ... using JDBC, bind that variable and run the SQL query

The problem is that lower-casing is a locale-specific operation. For example, lower-casing the letter “I” gives different results in English and Turkish. In the above code, there are two lower-casing operations:

• The String#toLowerCase() method
• The lower() database function

How can I make sure that Java and the database are using the same locale and thereby performing a valid comparison?

I’m aware that the String class has a toLowerCase(Locale) method, but how do I know what Locale the database is using? Can I check this programatically, or do I have to hard-code the locale to the one with which I think the database (in this case Oracle 10g) is configured?

Answer 1

The simple answer is let the database do it.
That way the way the bind variable is put into lower case will be consistent with the way the column value is put into lowercase.

String sql = "select * from Person where lower(name) = lower(?)";