Insert into Table by getting NextVal of Sequence in PostgreSQL - mysql

Question

I have a table called SEQ_TABLE which has two columns, SEQ_NAME and ID
SEQ_NAME | ID
----------------------
SEQ_TABLE_10 | 1
SEQ_TABLE_20 | 5
Where ID is the Max of COLUMN_1 of TABLE_10 and TABLE_20
Now, I have to Insert new records into TABLE_10 by obtaining nextvalue of sequence from SEQ_TABLE.
I have written PostgreSQL query as follows:
INSERT INTO TABLE_10 (COLUMN_1, COLUMN_2, COLUMN_3) VALUES ((SELECT nextval(SEQ_TABLE)), 'Bangalore' ,NULL);
When I execute above Query, It is giving below error:
********** Error **********
ERROR: column "SEQ_TABLE_10" does not exist
SQL state: 42703
Character: 99
But, following Query works fine in MySQL Database:
INSERT INTO TABLE_TABLE(COLUMN_1, COLUMN_2, COLUMN_3) VALUES ((SELECT nextval('TABLE_172_SEQ','true')), 'Bangalore' ,NULL);
What is the Exact Postgres Query to achieve it in PostgreSQL DB?

Answer 1

You want to create a sequence, not a table(SEQ_TABLE)
Kindly refer this link
https://www.postgresql.org/docs/8.1/static/sql-createsequence.html
Eg.
CREATE SEQUENCE serial START 101;
SELECT nextval('serial');
create table MyTable(col1 int,col2 varchar(20));
INSERT INTO MyTable VALUES (nextval('serial'), 'nothing');

Answer 2

In current PostgreSQL versions you would use identity columns:
CREATE TABLE table_10 (
id integer GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
other text NOT NULL
);
That will implicitly generate a sequence. You are not allowed to insert numbers into into id, but you have to
INSERT INTO table_10 (other) VALUES ('new');
or
INSERT INTO table_10 (id, other) VALUES (DEFAULT, 'new');
and id is automatically filled with the next value from the sequence.
On older PostgreSQL versions, you would use serial or bigserial:
CREATE TABLE table_10 (id serial PRIMARY KEY, other text NOT NULL);
Then id is of type integer, a sequence table_10_id_seq is created and a nextval call is added to the DEFAULT clause of the id column.
You can examine this with \d in psql:
\d table_10
Table "laurenz.table_10"
Column | Type | Modifiers
--------+---------+-------------------------------------------------------
id | integer | not null default nextval('table_10_id_seq'::regclass)
other | text | not null
Indexes:
"table_10_pkey" PRIMARY KEY, btree (id)
Moreover, the sequence belongs to the table and will be dropped automatically when the table is dropped.
You insert rows omitting the id column like this:
INSERT INTO table_10 (other) VALUES ('something');
Then the DEFAULT values will be used.
If you want to do the same thing “on foot”, for example to use a different name or different starting values for the sequence, that would work like this:
CREATE TABLE table_10 (id integer PRIMARY KEY, other text NOT NULL);
CREATE SEQUENCE table_10_id_seq OWNED BY table_10.id;
ALTER TABLE table_10 ALTER id SET DEFAULT nextval('table_10_id_seq');