SQL–Select查询的多种⽅法    CREATE TABLE tbl_students
(
snumber char,
sname varchar(10)
)
CREATE TABLE tbl_curriculums
(
cnumber char,
cname varchar(15),
cteacher varchar(10)
)
CREATE TABLE tbl_relationships
(
snumber char,
cnumber char,
score varchar(3)
)
--Method 1 Good
SELECT S.sname
FROM
tbl_students S,
tbl_curriculums C,
tbl_relationships R
WHERE
S.snumber = R.snumber AND
Rumber = Cumber AND
--Method 2 Better
SELECT S.sname
FROM
tbl_students S
WHERE
S.snumber in
(
SELECT R.snumber
From
tbl_curriculums C,
tbl_relationships R
WHERE
Rumber = Cumber AND
)
-- Method 3 Best
SELECT S.sname
FROM
tbl_students S
INNER JOIN tbl_relationships R ON S.snumber = R.snumber INNER JOIN tbl_curriculums C ON Rumber = Cumber acher ='XU'queryselectorall用法

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