如下：一張訂單表多個欄位關聯使用者表：

1.連結串列查詢

SELECT cu.id AS 'id',cu.version AS 'version',cu.cid AS 'cid',cu.uid AS 'uid',cu.shopName AS 'shopName',cu.address AS 'address',
cu.totalPrice AS 'totalPrice',cu.orderType AS 'orderType',
cu.state AS 'state',cu.cCreateTime AS 'cCreateTime',cu.decorate AS 'decorate',cu.area AS 'area',cu.roomArea AS 'roomArea',
cu.machinePrice AS 'machinePrice',cu.caid AS 'caid',
cu.cooperationtypeid AS 'cooperationtypeid',cu.cooperationRebate AS 'cooperationRebate',cu.cooperationPrcie AS 'cooperationPrcie',
cu.machineDiscount AS 'machineDiscount',cu.alreadyPaid AS 'alreadyPaid',cu.updateTime AS 'updateTime',cu.cooperationdeposit AS 'cooperationdeposit',
cu.updateUserid AS 'updateUserid',cu.overseerId AS 'overseerId',cu.decorationQuotation AS 'decorationQuotation',cu.machineDeposit AS 'machineDeposit',
us1.uName AS 'serviceuName',us2.uName AS 'updateName'
FROM `customerorder` AS cu LEFT JOIN `userdetail` AS us1 ON us1.id=cu.uid LEFT JOIN `userdetail` AS us2 ON us2.id=cu.updateUserid

2.子查詢
SELECT cu.id AS 'id',cu.version AS 'version',cu.cid AS 'cid',cu.uid AS 'uid',cu.shopName AS 'shopName',cu.address AS 'address',
cu.totalPrice AS 'totalPrice',cu.orderType AS 'orderType',
cu.state AS 'state',cu.cCreateTime AS 'cCreateTime',cu.decorate AS 'decorate',cu.area AS 'area',cu.roomArea AS 'roomArea',
cu.machinePrice AS 'machinePrice',cu.caid AS 'caid',
cu.cooperationtypeid AS 'cooperationtypeid',cu.cooperationRebate AS 'cooperationRebate',cu.cooperationPrcie AS 'cooperationPrcie',
cu.machineDiscount AS 'machineDiscount',cu.alreadyPaid AS 'alreadyPaid',cu.updateTime AS 'updateTime',cu.cooperationdeposit AS 'cooperationdeposit',
cu.updateUserid AS 'updateUserid',cu.overseerId AS 'overseerId',cu.decorationQuotation AS 'decorationQuotation',cu.machineDeposit AS 'machineDeposit',
(SELECT uName FROM `userdetail` WHERE id=cu.uid) AS 'serviceuName',(SELECT uName FROM `userdetail` WHERE id=cu.updateUserid) AS 'updateName'
FROM `customerorder` AS cu

總結：

1，表關聯的效率要高於子查詢，因為子查詢走的是笛卡爾積
2，表關聯可能有多條記錄，子查詢只有一條記錄，如果需要唯一的列，最好走子查詢