DB2数据库中SQL语句中使用or和and的关键字的时候注意事项

--正确的SQL语句，查询结果：746
SELECT  COUNT(1)
FROM    EHR_BASE EB, EHR_HF_INDICATOR EHI
WHERE   EB.EHR_ID=EHI.EHR_ID
AND     EB.CANCELLED = ''
AND     EB.DEATH = ''
AND     EB.MOVED_OUT = ''
AND     EB.MNG_ORG_CODE LIKE '0203%'
AND     MNG_ORG_NAME = '北京市西城区新街口社区卫生服务中心'
AND     EB.CD_DIABETES_MELLITUS = ''
AND     (EHI.FBG >= 7 OR EHI.FBG = -1)/*血糖FBG>=7或者FBG=-1*/

--错误的SQL语句查询结果：123010267
SELECT  COUNT(1)
FROM    EHR_BASE EB, EHR_HF_INDICATOR EHI
WHERE   EB.EHR_ID=EHI.EHR_ID
AND     EB.CANCELLED = ''
AND     EB.DEATH = ''
AND     EB.MOVED_OUT = ''
AND     EB.MNG_ORG_CODE LIKE '0203%'
AND     MNG_ORG_NAME = '北京市西城区新街口社区卫生服务中心'
AND     EB.CD_DIABETES_MELLITUS = ''
AND     EHI.FBG >= 7 OR EHI.FBG = -1