What does decode mean in sql

The DECODE function in SQL is a conversion function that converts an input expression into a specified value based on given conditions. The syntax is as follows: DECODE(expression, value1, result1, value2, result2, ..., default_result) The DECODE function checks the conditions one by one, finds a match and returns the corresponding result, otherwise it returns the default result. Equivalent to the CASE WHEN statement, but more concise and easier to read.

DECODE function in SQL

Question: What is the DECODE function in SQL?

Answer: The DECODE function is a conversion function that converts an input expression into a specified value, depending on the given conditions.

Detailed description:

The syntax of the DECODE function is as follows:

<code>DECODE(expression, value1, result1, value2, result2, ..., default_result)</code>

Among them:

• expression: The expression to evaluate.
• value1, value2, ...: Conditions to be checked.
• result1, result2, ...: The value to be returned when the corresponding condition is true.
• default_result: The value to be returned when all conditions are false.

DECODE function checks the given conditions one by one. When a condition matching expression is found, it returns the corresponding result. If no matching condition is found, it returns default_result.

Example:

Suppose we have a column called "gender" whose value can be "M" (male) or "F" (female). We can use the DECODE function to convert the "gender" value to the following representation:

<code>SELECT DECODE(gender, 'M', 'Male', 'F', 'Female', 'Unknown') AS gender_display
FROM table_name;</code>

This query will return the following results:

##MMaleFFemaleNULLUnknown

gender	gender_display

Note: The DECODE function is equivalent to the CASE WHEN statement. However, the DECODE function is generally more concise and easier to read.

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