Re: currval, lastval, nextvar?

In response to Carol Walter :
> Hello,
>
> I want write a query that will insert a record in a person table,
> insert a record in a presentation table, and then insert a record into
> a bridge table that contains the keys of both of the newly created
> records from the other two tables. According to the documentation,
> takes the next number in the sequence and reports it. Both currval
> and lastval report the last value that was taken from the sequence,
> but both will produce errors if a "nextval" was not called in the
> current session. Does writing a record that automatically updates a
> sequence count as calling nextval?

Yes. You don't need call nextval.

You can do something like :

test=# create table t1(id serial primary key);
NOTICE: CREATE TABLE will create implicit sequence "t1_id_seq" for serial column "t1.id"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t1_pkey"
for table "t1"
CREATE TABLE
test=*# create table t2(id serial primary key);
NOTICE: CREATE TABLE will create implicit sequence "t2_id_seq" for serial column "t2.id"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey"
for table "t2"
CREATE TABLE
test=*# create table brige (i1 int references t1, i2 int references t2);
CREATE TABLE
test=*# insert into t1 values(default);
INSERT 0 1
test=*# insert into t2 values(default);
INSERT 0 1
test=*# insert into brige values (currval('t1_id_seq'), currval('t2_id_seq'));
INSERT 0 1
test=*# select * from brige ;
i1 | i2
----+----
1 | 1
(1 Zeile)

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Andreas Kretschmer
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