This question already has answers here:
How to delete or add column in SQLITE?
(23 answers)
Closed 2 years ago.
sqlite> .schema autor
CREATE TABLE autor (ID INTEGER PRIMARY KEY, NOME TEXT, CIDADE TEXT, ESTADO TEXT, TELEFONE TEXT, idade number);
sqlite> alter table autor drop idade;
Error: near "drop": syntax error
(Also tried to use DROP COLUMN instead of DROP).
Please help, is that a bug ?
You can't do this with SQLite, because it does not support dropping columns. This is a documented limitation (emphasis mine):
Only the RENAME TABLE, ADD COLUMN, and RENAME COLUMN variants of the ALTER TABLE command are supported. Other kinds of ALTER TABLE operations such as DROP COLUMN, ALTER COLUMN, ADD CONSTRAINT, and so forth are omitted.
A possible workaround is to recreate another table with the correct structure, then copy the data, drop the old table and rename the new table:
create table autor_new (
id integer primary key,
nome text,
cidade text,
estado text,
telefone text
);
insert into autor_new select id, nome, cidade, estado, telefone from autor;
drop table autor; -- back it up first!
alter table autor_new rename to autor;
Related
I have an exercises table with this schema:
CREATE TABLE exercises
(
id INTEGER NOT NULL,
name VARCHAR(255) NOT NULL,
workoutID INTEGER NOT NULL,
FOREIGN KEY (workoutID) REFERENCES workouts(id)
);
I want to delete the column workoutID but it won't let me delete it:
sqlite> ALTER TABLE exercises DROP workoutID;
Error: near "DROP": syntax error
Upon realizing I need to remove the constraints first I try:
sqlite> ALTER TABLE exercises DROP CONSTRAINT workoutID;
Error: near "DROP": syntax error
I followed this question to the letter: How to drop column with constraint?
But it doesn't work for me.
I can start over by dropping the whole table if I have to but I want to learn why this isn't working for me.
Any help and explanation is greatly appreciated.
I have a primary key column in my SQL table in PostgreSQL named "id". It is a "bigseries" column. I want to convert the column to a "UUID" column. It entered the below command in the terminal:
alter table people alter column id uuid;
and
alter table people alter column id uuid using (uuid_generate_v4());
but neither of them worked.
In both tries I got the error message
ERROR: syntax error at or near "uuid"
LINE 1: alter table people alter column id uuid using (uuid_generate...
What is the correct syntax?
First of all uuid_generate_v4() is a function which is provided by an extension called uuid-ossp. You should have install that extension by using;
CREATE EXTENSION uuid-ossp;
Postgresql 13 introduced a new function which does basically the same without installing extension. The function is called gen_random_uuid()
Suppose that we have a table like the one below;
CREATE TABLE people (
id bigserial primary key,
data text
);
The bigserial is not a real type. It's a macro which basically creates bigint column with default value and a sequence. The default value is next value of that sequence.
For your use case, to change data type, you first should drop the old default value. Then, alter the type and finally add new default value expression. Here is the sample:
ALTER TABLE people
ALTER id DROP DEFAULT,
ALTER id TYPE uuid using (gen_random_uuid() /* or uuid_generate_v4() */ ),
ALTER id SET DEFAULT gen_random_uuid() /* or uuid_generate_v4() */ ;
CREATE TABLE IF NOT EXISTS people (
id uuid NOT NULL CONSTRAINT people_pkey PRIMARY KEY,
address varchar,
city varchar(255),
country varchar(255),
email varchar(255),
phone varchar(255)
);
This is the correct syntax to create table in postgres SQL, it's better to do these constraints at beginning to avoid any error.
For using alter command you would do the following:
ALTER TABLE customer ADD COLUMN cid uuid PRIMARY KEY;
Most of errors that you could find while writing command either lower case or undefined correct the table name or column.
This question already has an answer here:
A CREATE statement with quoted fields in Oracle
(1 answer)
Closed 1 year ago.
This is my device table
CREATE TABLE "DEVICE" (
"IMEI_Number" varchar(15),
"Device_Model" varchar(30),
"Device_Description" varchar(500),
"Assigned_Sim_Number" varchar(11),
"Activation_Date" timestamp,
"Deactivation_Date" timestamp,
"Manufacturer_ID" int,
"Customer_ID" int,
PRIMARY KEY ("IMEI_Number")
);
Then I have the manufacturer table which is
CREATE TABLE "MANUFACTURER" (
"Manufacturer_ID" int,
"Manufacturer_Name" varchar(30),
PRIMARY KEY ("Manufacturer_ID")
);
and I trying to create a relationship between these and getting the ORA-00904: "MANUFACTURER_ID": invalid identifier
My relationship code is
ALTER TABLE DEVICE
ADD FOREIGN KEY (Manufacturer_ID) REFERENCES MANUFACTURER(Manufacturer_ID);
That's just awful. Don't use double quotes when creating objects in Oracle as you'll have to use them every time you reference those objects, and match letter case every time.
SQL> alter table device add constraint fk_mf foreign key ("Manufacturer_ID")
2 references manufacturer ("Manufacturer_ID");
Table altered.
SQL>
A better option would be
SQL> create table device (
2 imei_number varchar2(15),
3 device_model varchar2(30),
4 device_description varchar2(500),
5 assigned_sim_number varchar2(11),
6 activation_date timestamp,
7 deactivation_date timestamp,
8 manufacturer_id int,
9 customer_id int,
10 primary key (imei_number)
11 );
Table created.
SQL> create table manufacturer (
2 manufacturer_id int,
3 manufacturer_name varchar2(30),
4 primary key (manufacturer_id)
5 );
Table created.
SQL> alter table device add constraint fk_mf foreign key (manufacturer_id)
2 references manufacturer (manufacturer_id);
Table altered.
SQL>
(Note also VARCHAR2 datatype; use that instead of VARCHAR).
By default, Oracle stores names in uppercase into data dictionary, but you can reference them using any case you want (upper, lower, mixed). If you do use double quotes, then you have to use their names exactly as during creation phase.
The columns in the tables you've created are surrounded by double-quotes, making their names case-sensitive, while the alter statement does not use quotes, and thus can't match the case-sensitive column name.
The best practice would be to drop these quotes and make the column names case-insensitive. If this is not an option, you could use the same quotes in the alter statement too:
ALTER TABLE DEVICE
ADD FOREIGN KEY ("Manufacturer_ID") REFERENCES MANUFACTURER("Manufacturer_ID");
-- Here ---------^---------------^--------------------------^---------------^
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'm, new to SQL. I have created few tables:
CREATE TABLE MAINTINANCE
(Maint_mname char(10),
Maint_date date,
Maint_duedate date NOT NULL,
Maint_mdesc char (15));
CREATE TABLE DESIGNERR
(Dez_emp_number varchar(11),
Dez_field char(12),
Dez_qualification char(10) NOT NULL,
Dez_experience smallint);
For the first table I am adding the following constraint:
ALTER TABLE MAINTINANCE ADD CONSTRAINT CHK_maintdate CHECK(Maint_date<MAint_duedate);
but I am getting the error invalid ALTER TABLE option. Could you please let me know why this is appearing? The same is working for a friend but not for me.
For the second table I have to write a SQL command for the business rule:
If the Qualification of a Designer is BS then a Minimum of 4 years
Experience is required. But, if the Qualification of the Designer is
MS then a Minimum of 2 years Experience is sufficient.
How can we define this business rule in SQL?
The code you posted works
SQL> CREATE TABLE MAINTINANCE
2 (Maint_mname char(10),
3 Maint_date date,
4 Maint_duedate date NOT NULL,
5 Maint_mdesc char (15));
Table created.
SQL> ALTER TABLE MAINTINANCE ADD CONSTRAINT CHK_maintdate CHECK(Maint_date<MAint_duedate);
Table altered.
If you're getting an error,
Cut and paste from a SQL*Plus session that shows exactly what statements you are executing
Post the full error stack
Although it does not affect your code, the word "MAINTINANCE" is misspelled. It should be "Maintenance". Future human developers will be grateful if your table names are spelled correctly.