使用子查询提高查询效率
故障现象：多查询一个字段时效率很低，少一个字段时效率快10倍
解决方案：使用子查询提高查询效率
实例：
SELECT
BTS.EMS_NE_NAME AS DEVICE_NAME,'3G' AS DEVICE_CATEGORY
,'光缆' AS COMPARE_TYP,SEG_ROAD.
OP_CABLE_SEG_NAME AS OBJ_NAME ,
--ROAD.OP_ROAD_NAME AS OBJ_OPTICAL,
CARR.CARRIER_OBJ_NAME, CARR.OBJ_NAME,CARR.OBJ_ID,
BTS.DATA_DOMAIN_ID,SEG_ROAD.
OP_CABLE_SEG_CODE,
(
SELECT ROAD.OP_ROAD_NAME FROM T_OP_ROAD ROAD WHERE (CARR.OBJ_ID = ROAD.OP_ROAD_ID)
) AS OBJ_OPTICAL,
CASE BTS.MARRY_STATE
WHEN 1
THEN '网管与资源匹配'
ELSE '资源缺失'
END
AS RES_STATUS,
CASE
WHEN (BTS.EMS_NE_NAME IS NULL OR
SEG_ROAD.OP_CABLE_SEG_ID IS NULL)
THEN '关联失败'
ELSE '关联成功'
END
AS "COMPARE_RESULT",'' AS TOWER_NAME,'' AS TOWER_CODE
FROM
T_WX_BTS BTS
LEFT JOIN T_WX_CARRIER CARR
ON (CARR.CARRIER_OBJ_ID=BTS.RES_NE_ID AND
OBJ_TYPE=8)
--LEFT JOIN T_OP_ROAD ROAD ON (CARR.OBJ_ID = ROAD.OP_ROAD_ID)
LEFT JOIN T_CABLESEG_RE_ROAD SEG_ROAD
ON(SEG_ROAD.OP_ROAD_ID=CARR.OBJ_ID)
WHERE
BTS.MARRY_STATE IN(1,2)
AND BTS.DATA_DOMAIN_ID IN (1030005,1070001,1030001,1150001,1010003,1060001,1050001,1090001,1140001,1080001,1020001,1040001,1100001,1020003,1010004)