如何使用sql解决case语句中的重复问题

SELECT DISTINCT
    CASE
        WHEN condition1 THEN value1
        WHEN condition2 THEN value2
        ...
        ELSE default_value
    END
FROM table_name;

SELECT column1, column2, ...,
    (SELECT 
        CASE
            WHEN condition1 THEN value1
            WHEN condition2 THEN value2
            ...
            ELSE default_value
        END
    FROM table_name AS sub_table
    WHERE sub_table.id = main_table.id) AS result
FROM main_table
GROUP BY column1, column2, ...;

SELECT
    CASE
        WHEN condition1 THEN SUM(value1)
        WHEN condition2 THEN COUNT(value2)
        ...
        ELSE default_value
    END AS result,
    other_column1, other_column2, ...
FROM table_name
GROUP BY other_column1, other_column2, ...;