Database Testing – Need and How to?

Why Database testing is required?

It is important to test the DATA ACCESS layer, since it is the interface between the front end and the DB.

The traditional testing always focused on the FRONT END/ GUI and the DATA ACCESS layer was ignored.

Structured Query Language (SQL) – Understanding Table JOINS

Structured Query Language (SQL) – Understanding Table JOINS

1)      INNER JOIN

The inner join is given as

SELECT d.Dept_name, e.emp_name

FROM Department  d

INNER JOIN employee e

ON d.dept_id = e.dept_id

Structured Query Language (SQL) – Using the UNION / UNION ALL

Structured Query Language (SQL) – Using the UNION / UNION ALL

In this case, let’s consider the tables such that it will be easier to understand the intricacies of the Union.

Table DEPARTMENT contains the Dept_ID and the Dept_name.

Table EMPLOYEE contains the Emp_ID, emp_name, incentives, deductions  and contains the details for the permanent employees.

Table TEMP_EMPLOYEE contains the EMP_ID, emp_name and contains the details for temporary employees. The tables have been segregated to understand the UNION query.