Oracle的DECODE函数

DECODE函数

语法格式
decode(字段或字段的运算，值1，值2，值3）

语法说明
当字段或字段的运算的值，等于值1时，该函数返回值2，否则返回值3
值1，值2，值3也可以是表达式

SELECT
    NVL (
        (
            DECODE (
                '2',
                (
                    SELECT
                        BIZ_ITEM_TYPE
                    FROM
                        DIC_ASSAY_BUSINESS_ITEM
                    WHERE
                        ID = ASSAY_BIZ_ITEM_ID
                ),
                (
                    SELECT
                        ASSAY_ITEM_NAME
                    FROM
                        DIC_ASSAY_ITEM
                    WHERE
                        ID = (
                            SELECT
                                BIZ_ITEM_ID
                            FROM
                                DIC_ASSAY_BUSINESS_ITEM
                            WHERE
                                ID = ASSAY_BIZ_ITEM_ID
                        )
                ),
                (
                    SELECT
                        BIZ_TASK_NAME
                    FROM
                        DIC_BUSINESS_TASK
                    WHERE
                        ID = (
                            SELECT
                                BIZ_ITEM_ID
                            FROM
                                DIC_ASSAY_BUSINESS_ITEM
                            WHERE
                                ID = ASSAY_BIZ_ITEM_ID
                        )
                )
            )
        ),
        (
            SELECT
                NAME
            FROM
                DIC_ASSAY_ITEM_CATE
            WHERE
                ID = ASSAY_BIZ_ITEM_CATE_ID
        )
    ) AS catename,
    < INCLUDE refid = "Base_Column_List" />
FROM
    DIC_ASSAY_BIZ_ITEM_CHARGE
WHERE
    1 = 1