I have a table that I create independently, the primary key is set with the serial type and a sequence applied to the table, but when I try to insert a value a NULL CONSTRAINT error is thrown and the return looks like null was passed, am I missing something in the INSERT statement?
SQL for table generation:
DROP TABLE IF EXISTS public."Team" CASCADE;
CREATE TABLE public."Team" (
"IdTeam" serial PRIMARY KEY,
name text NOT null,
CONSTRAINT "pKeyTeamUnique" UNIQUE ("IdTeam")
);
ALTER TABLE public."Team" OWNER TO postgres;
DROP SEQUENCE IF EXISTS public."Team_IdTeam_seq" CASCADE;
CREATE SEQUENCE public."Team_IdTeam_seq"
AS integer
START WITH 1
INCREMENT BY 1
NO MINVALUE
NO MAXVALUE
CACHE 1;
ALTER TABLE public."Team_IdTeam_seq" OWNER TO postgres;
ALTER SEQUENCE public."Team_IdTeam_seq" OWNED BY public."Team"."IdTeam";
SQL for insert :
INSERT INTO public."Team" (name) values ('Manchester Untited');
The returning error:
ERROR: null value in column "IdTeam" violates not-null constraint
DETAIL: Failing row contains (null, Manchester Untited).
SQL state: 23502
I am baffled. Why are you trying to define your own sequence when the column is already defined as serial?
Second, a primary key constraint is already unique. There is no need for a separate unique constraint.
Third, quoting identifiers just makes the code harder to write and to read.
You can just do:
DROP TABLE IF EXISTS public.Team CASCADE;
CREATE TABLE public.Team (
IdTeam serial PRIMARY KEY,
name text NOT null
);
INSERT INTO public.Team (name)
VALUES ('Manchester Untited');
Dropping the sequence causes the default definition for the IdTeam column to be dropped. After recreating the sequence you will have to recreate the default definition.
Related
Table definition:
CREATE TABLE IF NOT EXISTS public.test
(
"Id" integer NOT NULL GENERATED ALWAYS AS IDENTITY (INCREMENT 1 START 1 MINVALUE 1 MAXVALUE 2147483647 CACHE 1),
"SomeColumn" character(100) COLLATE pg_catalog."default",
CONSTRAINT test_pkey PRIMARY KEY ("Id")
)
TABLESPACE pg_default;
ALTER TABLE IF EXISTS public.test
OWNER to postgres;
I am trying this query:
INSERT INTO public.test VALUES ('testData');
But PostgreSQL throws this error:
ERROR: invalid input syntax for type integer: "testData"
LINE 1: INSERT INTO public.test VALUES ('testData');
I know this is valid in SQL Server. Is there a way the achieve this behaviour in PostgreSQL?
I do not want to specify the column names. Columns are defined in the order, but the identity column does not exist in the query.
I want to not give the column names
That's a bad idea. You should always specify the target columns for an INSERT statement. Especially if you want to skip some, but not others.
However, if you insist on bad coding style, you can use the DEFAULT keyword
INSERT INTO public.test VALUES (DEFAULT, 'testData');
I need to ensure that the values in a column from a table are unique as part of a larger process.
I'm aware of the UNIQUE constraint, but I'm wondering if there is a better way to do the check.
I'm running the queries using psycopg2 so adding that tag on the off chance there's something in there that can help with this.
If the column is unique I can add a constraint. If the column is not unique adding the constraint will return an error.
If there is already a constraint of the same name a useful error is returned. in this case would prefer to just check for the existing constraint.
If the column is the primary key, the unique constraint can be added without error but in this case it would be preferable to just recognize that the column must be unique based on the primary key.
Code examples of this below.
DROP TABLE IF EXISTS unique_test;
CREATE TABLE unique_test (
pkey INT PRIMARY KEY,
unique_yes CHAR(1),
unique_no CHAR(1)
);
INSERT INTO unique_test (pkey, unique_yes, unique_no)
VALUES(1, 'a', 'a'),
(2, 'b', 'a');
CREATE UNIQUE INDEX CONCURRENTLY u_test_1 ON unique_test (unique_yes);
ALTER TABLE unique_test
ADD CONSTRAINT unique_target_1
UNIQUE USING INDEX u_test_1;
-- the above runs no problem
-- check what happens when column is not unique
CREATE UNIQUE INDEX CONCURRENTLY u_test_2 ON unique_test (unique_no);
ALTER TABLE unique_test
ADD CONSTRAINT unique_target_2
UNIQUE USING INDEX u_test_2;
-- returns:
-- SQL Error [23505]: ERROR: could not create unique index "u_test_2"
-- Detail: Key (unique_no)=(a) is duplicated.
CREATE UNIQUE INDEX CONCURRENTLY u_test_1 ON unique_test (unique_yes);
ALTER TABLE unique_test
ADD CONSTRAINT unique_target_1
UNIQUE USING INDEX u_test_1;
-- returns
-- SQL Error [42P07]: ERROR: relation "unique_target_1" already exists
-- test what happens if adding constrint to primary key column
CREATE UNIQUE INDEX CONCURRENTLY u_test_pkey ON unique_test (pkey);
ALTER TABLE unique_test
ADD CONSTRAINT unique_target_pkey
UNIQUE USING INDEX u_test_pkey;
-- this runs no problem but is inefficient.
If all you want to do is verify that values are unique, then use a query:
select unique_no, count(*)
from unique_test
group by unique_no
having count(*) > 1;
If it needs to be boolean output:
select not exists (
select unique_no, count(*)
from unique_test
group by unique_no
having count(*) > 1
);
If you just want a flag, you can use:
select count(*) <> count(distinct uniq_no) as duplicate_flag
from unique_test;
DELETE FROM
zoo x
USING zoo y
WHERE
x.animal_id < y.animal_id
AND x.animal = y.animal;
I think this is simpler, https://kb.objectrocket.com/postgresql/delete-duplicate-rows-in-postgresql-762 for reference
I am beginner in sql.I am using sqlplus to run the sql query .I used simple query but it shows an error like "MISSING RIGHT PARENTHESIS".My objective is to create the autoincrement primary key .Can anyone solve the error?Thanks in advance...
create table student(rollno int identity(1,1) primary key,
name varchar(20),marks int);
For Oracle, the rollno column could be defined as NUMBER(0010) and primary key.
Then you would need to add an ON INSERT trigger to populate rollno from a SEQUENCE. There are many samples of triggers and sequences on this site.
In oracle 12 you can use a identity column to automatically fill your ID
CREATE TABLE students
(
"ID" NUMBER GENERATED BY DEFAULT AS IDENTITY MINVALUE 1 MAXVALUE 9999999999
INCREMENT BY 1 START WITH 1 ,
"NAME" VARCHAR2(20),
"MARKS" NUMBER(2,0),
CONSTRAINT PK_STUDENTS PRIMARY KEY (ID) ENABLE
);
/
This creates a table without any triggers needed and automatically fills the id column (of not specified with a value) with the next number up to 99999...
If you're using oracle 11 and below, you need a trigger on insert and assign a value (custom_sequence.nextval) to the id column.
CREATE TABLE students
(
"ID" NUMBER(5,0) not null,
"NAME" VARCHAR2(20),
"MARKS" NUMBER(2,0),
CONSTRAINT PK_STUDENTS PRIMARY KEY (ID) ENABLE
);
/
CREATE SEQUENCE SEQ_STUDENTS INCREMENT BY 1 START WITH 1;
/
TRIGGER TC_students
before insert on students
for each row
begin
if (:new.id is null) then
select SEQ_students.nextval into :new.id from dual;
end if;
end;
/
And please use VARCHAR2.
I am trying to remove a UNIQUE constraint on a column for sqlite but I do not have the name to remove the constraint. How can I find the name of the UNIQUE constraint name to remove it.
Below is the schema I see for the table I want to remove the constraint
UNIQUE (datasource_name)
sqlite> .schema datasources
CREATE TABLE "datasources" (
created_on DATETIME NOT NULL,
changed_on DATETIME NOT NULL,
id INTEGER NOT NULL,
datasource_name VARCHAR(255),
is_featured BOOLEAN,
is_hidden BOOLEAN,
description TEXT,
default_endpoint TEXT,
user_id INTEGER,
cluster_name VARCHAR(250),
created_by_fk INTEGER,
changed_by_fk INTEGER,
"offset" INTEGER,
cache_timeout INTEGER, perm VARCHAR(1000), filter_select_enabled BOOLEAN, params VARCHAR(1000),
PRIMARY KEY (id),
CHECK (is_featured IN (0, 1)),
CHECK (is_hidden IN (0, 1)),
FOREIGN KEY(created_by_fk) REFERENCES ab_user (id),
FOREIGN KEY(changed_by_fk) REFERENCES ab_user (id),
FOREIGN KEY(cluster_name) REFERENCES clusters (cluster_name),
UNIQUE (datasource_name),
FOREIGN KEY(user_id) REFERENCES ab_user (id)
);
SQLite only supports limited ALTER TABLE, so you can't remove the constaint using ALTER TABLE. What you can do to "drop" the column is to rename the table, create a new table with the same schema except for the UNIQUE constraint, and then insert all data into the new table. This procedure is documented in the Making Other Kinds Of Table Schema Changes section of ALTER TABLE documentation.
I just ran into this myself. An easy solution was using DB Browser for SQLite
It let me remove a unique constraint with just a checkbox in a gui.
PRAGMA foreign_keys=off;
BEGIN TRANSACTION;
ALTER TABLE table_name RENAME TO old_table;
CREATE TABLE table_name
(
column1 datatype [ NULL | NOT NULL ],
column2 datatype [ NULL | NOT NULL ],
...
);
INSERT INTO table_name SELECT * FROM old_table;
COMMIT;
PRAGMA foreign_keys=on;
Source: https://www.techonthenet.com/sqlite/unique.php
I was just working through this issue on a small database and found it easier to dump the data as SQL statements, it prints out your tables exactly as they are and also adds the INSERT INTO statements to rebuild the DB.
The .help terminal command shows:
.dump ?OBJECTS? Render database content as SQL
and prints the SQL to the terminal, you can update it in a TXT file. For once off changes and tidying this seems like a reasonable solution albeit a little inelegant
I'd like to add a NOT NULL column to a Redshift table that has records, an IDENTITY field, and that other tables have foreign keys to.
In PostgreSQL, you can add the column as NULL, fill it in, then ALTER it to be NOT NULL.
In Redshift, the best I've found so far is:
ALTER TABLE my_table ADD COLUMN new_column INTEGER;
-- Fill that column
CREATE TABLE my_table2 (
id INTEGER IDENTITY NOT NULL SORTKEY,
(... all the fields ... )
new_column INTEGER NOT NULL,
PRIMARY KEY(id)
) DISTSTYLE all;
UNLOAD ('select * from my_table')
to 's3://blah' credentials '<aws-auth-args>' ;
COPY my_table2
from 's3://blah' credentials '<aws-auth-args>'
EXPLICIT_IDS;
DROP table my_table;
ALTER TABLE my_table2 RENAME TO my_table;
-- For each table that had a foreign key to my_table:
ALTER TABLE another_table ADD FOREIGN KEY(my_table_id) REFERENCES my_table(id)
Is this the best way of achieving this?
You can achieve this w/o having to load to S3.
modify the existing table to create the desired column w/ a default value
update that column in some way (in my case it was copying from another column)
create a new table with the column w/o a default value
insert into the new table (you must list out the columns rather than using (*) since the order may be the same (say if you want the new column in position 2)
drop the old table
rename the table
alter table to give correct owner (if appropriate)
ex:
-- first add the column w/ a default value
alter table my_table_xyz
add visit_id bigint NOT NULL default 0; -- not null but default value
-- now populate the new column with whatever is appropriate (the key in my case)
update my_table_xyz
set visit_id = key;
-- now create the new table with the proper constraints
create table my_table_xzy_new
(
key bigint not null,
visit_id bigint NOT NULL, -- here it is not null and no default value
adt_id bigint not null
);
-- select all from old into new
insert into my_table_xyz_new
select key, visit_id, adt_id
from my_table_xyz;
-- remove the orig table
DROP table my_table_xzy_events;
-- rename the newly created table to the desired table
alter table my_table_xyz_new rename to my_table_xyz;
-- adjust any views, foreign keys or permissions as required