How to use if in sql

IF statement is used for conditional execution in SQL. Its syntax is: IF condition THEN true_statement [ELSE false_statement] END IF; usage includes: selecting and executing different SQL statement blocks based on conditions, such as dynamically displaying messages based on age. , update records, delete records or set variables.

Usage of IF in SQL

IF statement is used for conditional execution in SQL, allowing execution based on specified conditions Execute different blocks of SQL statements. Its basic syntax is as follows:

<code class="sql">IF (condition)
    THEN
        true_statement
[ELSE]
    false_statement
END IF;</code>

Usage instructions:

1. ##Condition (condition): A Boolean expression used to evaluate the condition authenticity.
2. True statement block (true_statement): SQL statement executed if the condition is true.
3. False statement block (false_statement) (optional): SQL statement to be executed if the condition is false.

Example:

customers which contains the following data:

<code class="sql">SELECT * FROM customers
WHERE age > 25;</code>

<code class="sql">SELECT id, name,
    CASE
        WHEN age > 25 THEN 'Eligible for VIP discount'
        ELSE 'Not eligible for VIP discount'
    END AS eligibility
FROM customers;</code>

Result:

Update records:

Delete records:
• DELETE FROM table_name WHERE condition;
Set variables:
• SET @variable_name = expression WHERE condition;

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