Database

How to speedup the execution of a query in Sql Server?

EmployeeId INT, FirstName VARCHAR, SurName VARCHAR, SexId INT 

SexId INT, Sex VARCHAR
-- Values inserted
-- 1, Male
-- 2, Female

EmployeeId INT, Contact VARCHAR -- may or may not be null AND can contain multiple values

SELECT ED.EmployeeId, ED.FirstName, ED.SurName, GROUP_CONCAT(EC.Contact) 
FROM EmployeeDetails ED, EmployeeSex ES, EmployeeContacts EC
WHERE ED.SexId = ES.SexId AND ED.EmployeeId = EC.EmployeeId AND ED.EmployeeId = 'emp_password';

Hi.

I have to choose between MySQL and PostgreSQL. I like use MS SQL, but it expensive for the customer.
Database have about 100 tables with max. 200 thousands rows.
Front application is .NET (winform) ,dataset or entity framework.

It's critical application, reliability is required.

Please advice me.

Karol

Procedure execution failed
1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '")' at line 1

CREATE DEFINER=<code>root</code>@<code>127.0.0.1</code> PROCEDURE <code>sp_populate_memo_country_companies</code>(IN param_country varchar(255))
BEGIN
    SELECT locations.location_id, companies.company_name, locations.location_name, first_payroll, last_payroll
    FROM locations
    JOIN country ON country.country_code_alpha2 = locations.country_code
    JOIN companies ON companies.company_id = locations.company_id
    LEFT JOIN payroll ON payroll.location_id = locations.location_id
    WHERE locations.country_code IN (param_country) AND payroll_active = TRUE
    GROUP BY locations.location_id
    ORDER BY companies.company_name;
END