MySQL中对表连接查询的简单优化教程

SELECT *
FROM a,b LEFT JOIN c ON (c.key=a.key) LEFT JOIN d ON (d.key=a.key)
WHERE b.key=d.key;

SELECT *
FROM b,a LEFT JOIN c ON (c.key=a.key) LEFT JOIN d ON (d.key=a.key)
WHERE b.key=d.key;

SELECT * FROM t1 LEFT JOIN t2 ON (column1) WHERE t2.column2=5;

SELECT * FROM t1, t2 WHERE t2.column2=5 AND t1.column1=t2.column1;

SELECT M.*,SS.SensorCode,SS.SensorStatus,SS.ManufacturerId,SS.Electricity,
SS.Voltage,SS.MinElectricity,SS.MinVoltage,SS.Temperature,SS.StatusUpdteDate,SS.UpdateStatus ,tp.PricingStrategyid,tps.FreeDuration,bat.BerthTypeId 
FROM
(SELECT T.* , BS.ParkStatus,BS.ChangeTime ,CA.CantonName, SE.SectionName
 FROM
(SELECT A.* ,B.BerthId,B.BerthCode,B.BerthAddress,B.BerthStatus,B.LineDirection,B.CantonId,B.SectionId 
FROM 
(SELECT AR.AreaId,AR.AreaCode,AR.AreaName FROM  SYS_Area AS AR WHERE 1=1  AND AR.AreaCode='110' ) A 
LEFT JOIN SYS_Berth AS B ON B.AreaId=A.AreaId ) T
JOIN SYS_BerthStatus AS BS ON T.BerthCode=BS.BerthCode 
JOIN SYS_Canton AS CA ON T.CantonId=CA.CantonId 
JOIN SYS_Section AS SE ON T.SectionId=SE.SectionId )M

LEFT JOIN SYS_Sensor SS ON M.BerthCode=SS.BerthCode 
LEFT JOIN TRA_PricingBerth AS tp ON tp.BerthCode=M.BerthCode 
 
LEFT JOIN TRA_PricingStrategy AS tps ON tps.PricingStrategyId=tp.PricingStrategyId 
LEFT JOIN SYS_BerthAndType AS bat ON bat.BerthCode=M.BerthCode 
ORDER BY BerthCode ASC