Hi

My databases in mysql or mssql contains Greek characters.
But when I execute a query the result shows any other
character except Greek.

How I can solve this problem?

for MSSQL, try to find a different forum; MSSQL support in HeidiSQL is experimental, and mostly unsupported.

For MySQL, first of all, you can start solving this problem by providing a lot more of information about your system if you expect a sensible answer.
- what do you see instead of the expected greek characters ?
- what is the version of the mysql server you are using ? (SELECT @@version, SELECT version())
- for a database xxx where the problem occurs, what is the databases´ default character set ? (is included in result of SHOW CREATE DATABASE xxx)
- for a table yyy within xxx, where the problem occurs, what is the table´s character set ? (is included in result of SHOW CREATE TABLE xxx, as DEFAULT CHARSET= near the end, unless identical to default from xxx)
- for a field within the table yyy, where the problem occurs, does the field have a specific character set assigned which is different from its containing table ?
- what does SELECT @@character_set_client,@@character_set_connection,@@character_set_results return ?
- did you insert the field values from heidisql, or from some other tool or web interface (?php) ?

also, reading this might help; it appears complicated, but then, this is a complex subject (unless all your characer set settings are utf8, which probably is the best solution anyhow).