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【DM版本】: DM8
【操作系统】：linux
【CPU】: 16核
【问题描述】*：
我的sql中用一个if没有问题：

set schema  mycommunity_szjgxctest;
SELECT
    COUNT(*) 
FROM
    (
    SELECT
        "proj"."name" AS "proj_name",
    IF
        ((
            SELECT "online_status" FROM "q_aiot_norm_device_online_status" AS "o" 
            WHERE "o"."device_id" = "iot"."id" 
            ORDER BY "occurrence_time" DESC LIMIT 1 
                ) IS NULL,
            0,(
            SELECT "online_status" FROM "q_aiot_norm_device_online_status" AS "o"  WHERE
                "o"."device_id" = "iot"."id" 
            ORDER BY
                "occurrence_time" DESC 
                LIMIT 1 
            )) AS "status",
        "iot"."type_code" AS "device_code",
        "iot"."created_on" AS "created_on" 
    FROM
        "q_aiot_norm_device" "iot"
        LEFT JOIN "t_project" "proj" ON "iot"."proj_id" = "proj"."id" 
    WHERE
    ( "iot"."is_deleted" = 1 )) "d"

而包含了两个if就会报无法解析的成员访问表达式 IF

set schema  mycommunity_szjgxctest;
SELECT
    COUNT(*) 
FROM
    (
    SELECT
        "proj"."name" AS "proj_name",
    IF
        ((
            SELECT "online_status" FROM "q_aiot_norm_device_online_status" AS "o" 
            WHERE "o"."device_id" = "iot"."id" 
            ORDER BY "occurrence_time" DESC LIMIT 1 
                ) IS NULL,
            0,(
            SELECT "online_status" FROM "q_aiot_norm_device_online_status" AS "o"  WHERE
                "o"."device_id" = "iot"."id" 
            ORDER BY
                "occurrence_time" DESC 
                LIMIT 1 
            )) AS "status",
    IF
        ((
            SELECT "occurrence_time" FROM "q_aiot_norm_device_online_status" AS "o" WHERE "o"."device_id" = "iot"."id" 
            ORDER BY "occurrence_time" DESC LIMIT 1 
                ) IS NULL,
            0,(
            SELECT "occurrence_time" FROM "q_aiot_norm_device_online_status" AS "o" 
            WHERE
                "o"."device_id" = "iot"."id" 
            ORDER BY
                "occurrence_time" DESC 
                LIMIT 1 
            )) AS "status_time",
        "iot"."type_code" AS "device_code",
        "iot"."created_on" AS "created_on" 
    FROM
        "q_aiot_norm_device" "iot"
        LEFT JOIN "t_project" "proj" ON "iot"."proj_id" = "proj"."id" 
    WHERE
    ( "iot"."is_deleted" = 1 )) "d"