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Asked: 2024-09-26T19:45:12+05:30 In:

how to use if else in sql query

I’m currently working on a SQL project, and I’m a bit confused about how to implement conditional logic within my queries. I understand that sometimes I need to display different results based on specific conditions, but I’m not quite sure how to structure my SQL statements using “IF” and “ELSE”.

For example, let’s say I have a table with employee data, and I want to categorize employees based on their salaries. I want to display “High Salary” for anyone earning above $80,000, “Medium Salary” for those between $50,000 and $80,000, and “Low Salary” for anyone earning below $50,000. How can I do this within a single query?

I’ve tried using CASE statements, but I’m not entirely sure if that’s the correct approach or if it functions similarly to an “IF-ELSE” statement in programming languages. Furthermore, I’m also confused about where to place this logic — should it be in the SELECT clause, or is there a different part of the SQL query where it should go? Any clarifications or examples would be greatly appreciated!

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    2 Answers

    1. Using IF ELSE in SQL Queries

      Okay, so you wanna do some IF ELSE stuff in SQL? Here’s a simple way to think about it!

      Imagine you have a table called students and you want to check if a student passed or failed based on their score. If the score is 60 or more, they passed; otherwise, they failed.

      Here’s a simple example:

              SELECT name,
            CASE 
                WHEN score >= 60 THEN 'Passed'
                ELSE 'Failed'
            END AS result
        FROM students;

      So, what’s happening here?

      • SELECT name – We’re picking the name of the student.
      • CASE – This is like starting your IF ELSE.
      • WHEN score >= 60 THEN 'Passed' – This is the IF part; if score is 60 or more, it says ‘Passed’.
      • ELSE 'Failed' – If the score isn’t 60 or more, it says ‘Failed’.
      • END AS result – This ends the CASE statement and names our new column as result.

      Just put the above query into your SQL editor and run it! You’ll see whether the students passed or failed based on their scores. Easy peasy!


    2. To use conditional logic such as “if else” in SQL queries, you can utilize the `CASE` statement, which operates similarly to a switch statement in other programming languages. The `CASE` statement allows you to execute specific logic based on certain conditions within a query. For example, the syntax is structured as follows: `
      `
      “`sql
      SELECT column1,
      column2,
      CASE
      WHEN condition1 THEN result1
      WHEN condition2 THEN result2
      ELSE default_result
      END as alias_name
      FROM table_name;
      “`
      In this structure, you evaluate each condition in sequence until a match is found, executing the corresponding result. If none of the conditions are met, the result from the `ELSE` clause is returned.

      The `CASE` statement can be employed in various parts of your SQL query, including `SELECT`, `ORDER BY`, and even `WHERE` clauses. For instance, you might want to categorize data based on sales performance in a `SELECT` statement: `
      `
      “`sql
      SELECT employee_id,
      sales,
      CASE
      WHEN sales >= 100000 THEN ‘High Performer’
      WHEN sales >= 50000 THEN ‘Average Performer’
      ELSE ‘Low Performer’
      END as performance_level
      FROM sales_data;
      “`
      This flexibility allows for robust data manipulation and analysis, akin to the control structures found in many programming languages. Keep in mind that the readability of your SQL queries can significantly enhance maintainability, so use the `CASE` statement wisely to avoid overly complex conditions.

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