Tag Archives: structured query language

SQL Query Optimization Techniques and Tips

SQL Query Optimization Tips

The most important part and parcel of a Database management system is the SQL. It will differ from product to product. Given below are some tips on how to write a well optimized query and avoid performance bottlenecks.

Primary verification of the SQL.

1)       The SQL query will need to be verified by two parameters

  1. The SQL returns the appropriate results.
  2. The SQL adequately addresses the issues of optimization and efficiency. Continue reading SQL Query Optimization Techniques and Tips

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

Continue reading Structured Query Language (SQL) – Understanding Table JOINS

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.

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

Structured Query Language (SQL) – Using GROUP BY/ HAVING

Structured Query Language – Using Group By/ Having

The GROUP BY query is typically used with aggregates.

SELECT d.dept_name, d.location, count(e.emp_ID)

FROM department d, employee e

WHERE d.dept_id = e.dept_id

GROUP BY d.dept_name, d.location

Continue reading Structured Query Language (SQL) – Using GROUP BY/ HAVING