MySQL插入數據前檢測唯一性

說明：mysql在插入數據的時候檢查數據的唯一性，符合條件的數據存在的話不插入，不存在的話插入數據，下面是書寫示例：

INSERT INTO digital_index_warning_history(
        monitor_point_name,
        device_name,
        param_name,
        value,
        warning_type,
        l_limit,
        ll_limit,
        lll_limit,
        h_limit,
        hh_limit,
        hhh_limit,
        warning_pri,
        created_at)
        SELECT
        #{monitorPointName},
        #{deviceName},
        #{paramName},
        #{value},
        #{warningType},
        #{lLimit},
        #{llLimit},
        #{lllLimit},
        #{hLimit},
        #{hhLimit},
        #{hhhLimit},
        #{warningPri},
        now()
        FROM dual WHERE NOT EXISTS
        (SELECT recovered_at
        FROM
        digital_index_warning_history
        WHERE
        monitor_point_name=#{monitorPointName}
        AND param_name=#{paramName}
        AND recovered_at IS NULL
        )