Thread: Replacing a table with constraints

I have a table called Counties which partially contains a lot bad data.  By" bad data", I mean some records are
missing;some exist and shouldn't; and some records have fields with erroneous information.  However, the majority of
thedata in the table is accurate.  I have built/loaded a new table called newCounties with the same structure as
Counties,but contains no bad data.  My was  to completely replace the contents of Counties with the contents of
newCounties. The problem is: several other tables have Foreign Key constraints placed on Counties.  Therefore, Pg will
notlet me 'DELETE FROM Counties;", nor will it let me "DROP TABLE Counties;"  <br /><br /> I'm perplexed.  Can someone
suggesthow I can best get data from Counties to look just like newCounties?<br /><br /> Mark<br /> 

From: Mark Fenbers

To: pgsql-sql@postgresql.org

Sent: Friday, May 13, 2005 2:38 PM

Subject: [SQL] Replacing a table with constraints

I have a table called Counties which partially contains a lot bad data.  By" bad data", I mean some records are missing; some exist and shouldn't; and some records have fields with erroneous information.  However, the majority of the data in the table is accurate.  I have built/loaded a new table called newCounties with the same structure as Counties, but contains no bad data.  My was  to completely replace the contents of Counties with the contents of newCounties.  The problem is: several other tables have Foreign Key constraints placed on Counties.  Therefore, Pg will not let me 'DELETE FROM Counties;", nor will it let me "DROP TABLE Counties;" 

I'm perplexed.  Can someone suggest how I can best get data from Counties to look just like newCounties?

Mark

---

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TIP 8: explain analyze is your friend

True, but Counties has about 8 or 9 rules, view, or pk constraints attached to it.  I don't want to break all these
unlessI knew of a way to save off the SQL for them beforehand so I can easily rebuild them...<br /> Mark<br /><br />
Ing.Jhon Carrillo wrote: <blockquote cite="mid01c301c557ec$9983b090$1400a8c0@tgusta2"
type="cite"><style></style><div><fontcolor="#000000" face="Arial" size="2">Use          Drop table YOUR_TABLE
<strong>cascade</strong></font></div><div> </div><div><fontcolor="#000000">Jhon Carrillo<br /> Ingeniero en
Computación<br/></font><font color="#000000">Caracas - Venezuela<br /></font></div><div> </div><div> </div><div>-----
OriginalMessage ----- </div><blockquote style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px; padding-left:
5px;margin-left: 5px; margin-right: 0px;"><div style="background: rgb(228, 228, 228) none repeat scroll 0%;
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arial;font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal;
font-size-adjust:none; font-stretch: normal;"><b>From:</b> <a href="mailto:Mark.Fenbers@noaa.gov"
title="Mark.Fenbers@noaa.gov">MarkFenbers</a></div><div style="font-family: arial; font-style: normal; font-variant:
normal;font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch:
normal;"><b>To:</b><a href="mailto:pgsql-sql@postgresql.org"
title="pgsql-sql@postgresql.org">pgsql-sql@postgresql.org</a></div><divstyle="font-family: arial; font-style: normal;
font-variant:normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch:
normal;"><b>Sent:</b>Friday, May 13, 2005 2:38 PM</div><div style="font-family: arial; font-style: normal;
font-variant:normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch:
normal;"><b>Subject:</b>[SQL] Replacing a table with constraints</div><div><br /></div> I have a table called Counties
whichpartially contains a lot bad data.  By" bad data", I mean some records are missing; some exist and shouldn't; and
somerecords have fields with erroneous information.  However, the majority of the data in the table is accurate.  I
havebuilt/loaded a new table called newCounties with the same structure as Counties, but contains no bad data.  My was 
tocompletely replace the contents of Counties with the contents of newCounties.  The problem is: several other tables
haveForeign Key constraints placed on Counties.  Therefore, Pg will not let me 'DELETE FROM Counties;", nor will it let
me"DROP TABLE Counties;"  <br /><br /> I'm perplexed.  Can someone suggest how I can best get data from Counties to
lookjust like newCounties?<br /><br /> Mark<br /><p><hr /><br /> ---------------------------(end of
broadcast)---------------------------<br/> TIP 8: explain analyze is your friend<br /></blockquote></blockquote> 

Are the constraints deferrable?

If they are, then you can replace the data with a single transaction.

If not, then you'll have to look at disabling triggers for the update.

On Fri, 2005-05-13 at 14:55, Mark Fenbers wrote:
> True, but Counties has about 8 or 9 rules, view, or pk constraints
> attached to it.  I don't want to break all these unless I knew of a
> way to save off the SQL for them beforehand so I can easily rebuild
> them...
> Mark
>
> Ing. Jhon Carrillo wrote:
> > Use          Drop table YOUR_TABLE cascade
> >
> > Jhon Carrillo
> > Ingeniero en Computación
> > Caracas - Venezuela
> >
> >
> >
> > ----- Original Message -----
> >         From: Mark Fenbers
> >         To: pgsql-sql@postgresql.org
> >         Sent: Friday, May 13, 2005 2:38 PM
> >         Subject: [SQL] Replacing a table with constraints
> >
> >         I have a table called Counties which partially contains a
> >         lot bad data.  By" bad data", I mean some records are
> >         missing; some exist and shouldn't; and some records have
> >         fields with erroneous information.  However, the majority of
> >         the data in the table is accurate.  I have built/loaded a
> >         new table called newCounties with the same structure as
> >         Counties, but contains no bad data.  My was  to completely
> >         replace the contents of Counties with the contents of
> >         newCounties.  The problem is: several other tables have
> >         Foreign Key constraints placed on Counties.  Therefore, Pg
> >         will not let me 'DELETE FROM Counties;", nor will it let me
> >         "DROP TABLE Counties;"
> >
> >         I'm perplexed.  Can someone suggest how I can best get data
> >         from Counties to look just like newCounties?
> >
> >         Mark
> >
> >
> >
> >         ____________________________________________________________
> >         ---------------------------(end of
> >         broadcast)---------------------------
> >         TIP 8: explain analyze is your friend
>
>
> ______________________________________________________________________
> ---------------------------(end of broadcast)---------------------------
> TIP 6: Have you searched our list archives?
>
>                http://archives.postgresql.org

On Fri, 2005-05-13 at 14:38 -0400, Mark Fenbers wrote:
> I have a table called Counties which partially contains a lot bad
> data.  By" bad data", I mean some records are missing; some exist and
> shouldn't; and some records have fields with erroneous information.
> However, the majority of the data in the table is accurate.  I have
> built/loaded a new table called newCounties with the same structure as
> Counties, but contains no bad data.  My was  to completely replace the
> contents of Counties with the contents of newCounties.  The problem
> is: several other tables have Foreign Key constraints placed on
> Counties.  Therefore, Pg will not let me 'DELETE FROM Counties;", nor
> will it let me "DROP TABLE Counties;"  
> 
> I'm perplexed.  Can someone suggest how I can best get data from
> Counties to look just like newCounties?

assuming same primary key on these 2 tables, you have to
consider these cases:

a) records in Counties not in newCounties
b) records in newCounties existing in Counties, but different
c) records in newCounties also correct in Counties
d) records in newCounties missing from Counties

a) get rid of extra records:      delete from Counties              where primarykey not in                 (select
primarykeyfrom newCounties);  if you hit foreign key constrains, you need to look  at your data a bit more, anyways 
 
b) update erroneous records:      update Counties from newCounties set            col1= newCounties.col1,
col2=newCounties.col2,           col3= newCounties.col3,           ...      from newCounties      where
primarykey=newCounties.primarykey          and           (    Counties.col1 <> newCounties.col1             OR
Counties.col2<> newCounties.col2             OR Counties.col3 <> newCounties.col3             ... );
 

c) nothing to do here

d) insert into Counties       select * from newCounties          where primarykey not in             (select primarykey
fromCounties);
 



test case:

test=# create table c (p int, col1 int, col2 int);
CREATE TABLE
test=# insert into c values (1,1,1); -- correct values
INSERT 7693959 1
test=# insert into c values (2,1,2); -- incorrect
INSERT 7693960 1
test=# insert into c values (9,9,9); -- extra value
INSERT 7693961 1
test=# create table newc (p int, col1 int, col2 int);
CREATE TABLE
test=# insert into newc values (1,1,1); -- correct values
INSERT 7693964 1
test=# insert into newc values (2,2,2); -- incorrect in c
INSERT 7693965 1
test=# insert into newc values (3,3,3); -- missing in c
INSERT 7693966 1
test=# delete from c where p not in (select p from newc);
DELETE 1
test=# update c set col1=n.col1, col2=n.col2
test-#   from newc as n
test-#   where c.p=n.p and (c.col1<>n.col1 or c.col2<>n.col2);
UPDATE 1
test=# insert into c select * from newc where p not in (select p from
c);
INSERT 7693967 1
test=# select * from c;p | col1 | col2
---+------+------1 |    1 |    12 |    2 |    23 |    3 |    3
(3 rows)


note: 
b) and c) can be merged and simplified if you don't mind updating
unchanged records:      update Counties from newCounties set            col1= newCounties.col1,           col2=
newCounties.col2,          col3= newCounties.col3,           ...      from newCounties      where
primarykey=newCounties.primarykey;



gnari