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From: Jian He <hejian.mark@gmail.com>
Date: Wed, 6 Apr 2022 09:37:55 +0530
Message-ID: 
 <CAMV54g2OxGKMyuUVwNM0LdDZsvM7XJVbe4WmVRMLNTZ5X1d0Gg@mail.gmail.com>
Subject: Does postgresql know the check condition is valid or not. or can
 check deduce from multiple conditions
To: pgsql-sql <pgsql-sql@lists.postgresql.org>
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If the question is stupid, please tell me why.

postgresql - How to query check the constraint is valid or not - Stack
Overflow
<https://stackoverflow.com/questions/71746611/how-to-query-check-the-constraint-is-valid-or-not>
Postgres 14 | db<>fiddle (dbfiddle.uk)
<https://dbfiddle.uk/?rdbms=postgres_14&fiddle=8157a4c1823635980019f3bdb1fa6835>

CREATE TABLE emp (test_check int check ( test_check >1 and test_check
< 0 ));

alter table emp  VALIDATE CONSTRAINT emp_test_check_check;```

select * from pg_constraint where conname = 'emp_test_check_check';

Even with the above mentioned step, does postgresql know above check
constraint condition always false.


another similar question:
can postgresql deduce from
CREATE TABLE emp1 (test_check int check ( test_check >1 and test_check > 10
));

to

CREATE TABLE emp1 (test_check int check ( test_check > 10 ));

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<div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><p styl=
e=3D"color:rgb(0,0,0);font-family:helvetica;font-size:14px">If the question=
=C2=A0is stupid, please tell me why.=C2=A0</p><p style=3D"color:rgb(0,0,0);=
font-family:helvetica;font-size:14px"><a href=3D"https://stackoverflow.com/=
questions/71746611/how-to-query-check-the-constraint-is-valid-or-not">postg=
resql - How to query check the constraint is valid or not - Stack Overflow<=
/a><br><a href=3D"https://dbfiddle.uk/?rdbms=3Dpostgres_14&amp;fiddle=3D815=
7a4c1823635980019f3bdb1fa6835">Postgres 14 | db&lt;&gt;fiddle (dbfiddle.uk)=
</a><br></p><p style=3D"color:rgb(0,0,0);font-family:helvetica;font-size:14=
px">CREATE=C2=A0TABLE=C2=A0emp (test_check int=C2=A0check=C2=A0( test_check=
 &gt;1=C2=A0and=C2=A0test_check &lt;=C2=A00=C2=A0));</p><p style=3D"color:r=
gb(0,0,0);font-family:helvetica;font-size:14px">alter table emp =C2=A0VALID=
ATE CONSTRAINT emp_test_check_check;```</p><p style=3D"color:rgb(0,0,0);fon=
t-family:helvetica;font-size:14px">select * from pg_constraint where connam=
e =3D &#39;emp_test_check_check&#39;;<br><br>Even with the above mentioned =
step, does postgresql know above check constraint condition always false.</=
p><p style=3D"color:rgb(0,0,0);font-family:helvetica;font-size:14px"><br>an=
other similar question:<br>can postgresql deduce from<br>CREATE TABLE emp1 =
(test_check int check ( test_check &gt;1 and test_check &gt; 10 ));</p><p s=
tyle=3D"color:rgb(0,0,0);font-family:helvetica;font-size:14px">to</p><p sty=
le=3D"color:rgb(0,0,0);font-family:helvetica;font-size:14px">CREATE TABLE e=
mp1 (test_check int check ( test_check &gt; 10 ));</p></div></div></div></d=
iv>

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