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
R.cnumber = C.cnumber AND
C.cteacher = 'XU'
--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
R.cnumber = C.cnumber AND
C.cteacher = 'XU'
)
-- 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 R.cnumber = C.cnumber
AND C.cteacher ='XU'
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