SQL - referential integrity - Foreign key and Check constraint
Please let me know if below two declarations are same.
create table R1
( a INT PRIMARY KEY,
b INT references K(w));
Note: K is a table with single attribute w as primary key
create table R1
( a INT PRIMARY KEY,
b INT CHECK (b in (SELECT w FROM K));
referential-integrity
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
asked Jun 16 '14 at 7:27
PhaniPhani
1
bumped to the homepage by Community♦ 17 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
add a comment |
Please let me know if below two declarations are same.
create table R1
( a INT PRIMARY KEY,
b INT references K(w));
Note: K is a table with single attribute w as primary key
create table R1
( a INT PRIMARY KEY,
b INT CHECK (b in (SELECT w FROM K));
referential-integrity
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
asked Jun 16 '14 at 7:27
PhaniPhani
1
bumped to the homepage by Community♦ 17 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
IfK(w)is a primary or unique key, they are similar declarations. But most SQL products accept only the first syntax (FOREIGN KEYconstraint) and not the second (which has a subquery in aCHECKconstraint)
– ypercubeᵀᴹ
Jun 16 '14 at 8:52
add a comment |
Please let me know if below two declarations are same.
create table R1
( a INT PRIMARY KEY,
b INT references K(w));
Note: K is a table with single attribute w as primary key
create table R1
( a INT PRIMARY KEY,
b INT CHECK (b in (SELECT w FROM K));
referential-integrity
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
asked Jun 16 '14 at 7:27
PhaniPhani
1
Please let me know if below two declarations are same.
create table R1
( a INT PRIMARY KEY,
b INT references K(w));
Note: K is a table with single attribute w as primary key
create table R1
( a INT PRIMARY KEY,
b INT CHECK (b in (SELECT w FROM K));
referential-integrity
referential-integrity
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
asked Jun 16 '14 at 7:27
PhaniPhani
1
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
asked Jun 16 '14 at 7:27
PhaniPhani
1
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
edited Jun 16 '14 at 8:50
ypercubeᵀᴹ
75.5k11128211
75.5k11128211
asked Jun 16 '14 at 7:27
PhaniPhani
1
asked Jun 16 '14 at 7:27
PhaniPhani
1
asked Jun 16 '14 at 7:27
PhaniPhani
1
1
bumped to the homepage by Community♦ 17 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
bumped to the homepage by Community♦ 17 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
IfK(w)is a primary or unique key, they are similar declarations. But most SQL products accept only the first syntax (FOREIGN KEYconstraint) and not the second (which has a subquery in aCHECKconstraint)
– ypercubeᵀᴹ
Jun 16 '14 at 8:52
add a comment |
IfK(w)is a primary or unique key, they are similar declarations. But most SQL products accept only the first syntax (FOREIGN KEYconstraint) and not the second (which has a subquery in aCHECKconstraint)
– ypercubeᵀᴹ
Jun 16 '14 at 8:52
If
K(w) is a primary or unique key, they are similar declarations. But most SQL products accept only the first syntax (FOREIGN KEY constraint) and not the second (which has a subquery in a CHECK constraint)– ypercubeᵀᴹ
Jun 16 '14 at 8:52
If
K(w) is a primary or unique key, they are similar declarations. But most SQL products accept only the first syntax (FOREIGN KEY constraint) and not the second (which has a subquery in a CHECK constraint)– ypercubeᵀᴹ
Jun 16 '14 at 8:52
add a comment |
1 Answer
1
active
oldest
votes
Not exactly - with your second CREATE statement, the same value of b can occur multiple times in table K, whereas with the first statement, it will occur once and once only. It's unusual - what are you trying to achieve?
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
add a comment |
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1 Answer
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Not exactly - with your second CREATE statement, the same value of b can occur multiple times in table K, whereas with the first statement, it will occur once and once only. It's unusual - what are you trying to achieve?
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
add a comment |
Not exactly - with your second CREATE statement, the same value of b can occur multiple times in table K, whereas with the first statement, it will occur once and once only. It's unusual - what are you trying to achieve?
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
add a comment |
Not exactly - with your second CREATE statement, the same value of b can occur multiple times in table K, whereas with the first statement, it will occur once and once only. It's unusual - what are you trying to achieve?
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
Not exactly - with your second CREATE statement, the same value of b can occur multiple times in table K, whereas with the first statement, it will occur once and once only. It's unusual - what are you trying to achieve?
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
answered Jun 16 '14 at 8:30
VéraceVérace
16k33350
16k33350
add a comment |
add a comment |
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If
K(w)is a primary or unique key, they are similar declarations. But most SQL products accept only the first syntax (FOREIGN KEYconstraint) and not the second (which has a subquery in aCHECKconstraint)– ypercubeᵀᴹ
Jun 16 '14 at 8:52