Develop Reference

change sqlite table column to be unique [duplicate]

How do I alter column in sqlite?
This is in Postgresql
ALTER TABLE books_book ALTER COLUMN publication_date DROP NOT NULL;
I believe there is no ALTER COLUMN in sqlite at all, only ALTER TABLE is supported.
Any idea? Thanks!

There's no ALTER COLUMN in sqlite.
I believe your only option is to:
Rename the table to a temporary name
Create a new table without the NOT NULL constraint
Copy the content of the old table to the new one
Remove the old table
This other Stackoverflow answer explains the process in details

While it is true that the is no ALTER COLUMN, if you only want to rename the column, drop the NOT NULL constraint, or change the data type, you can use the following set of dangerous commands:
PRAGMA writable_schema = 1;
UPDATE SQLITE_MASTER SET SQL = 'CREATE TABLE BOOKS ( title TEXT NOT NULL, publication_date TEXT)' WHERE NAME = 'BOOKS';
PRAGMA writable_schema = 0;
You will need to either close and reopen your connection or vacuum the database to reload the changes into the schema.
For example:
Y:\> **sqlite3 booktest**
SQLite version 3.7.4
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> **create table BOOKS ( title TEXT NOT NULL, publication_date TEXT NOT
NULL);**
sqlite> **insert into BOOKS VALUES ("NULLTEST",null);**
Error: BOOKS.publication_date may not be NULL
sqlite> **PRAGMA writable_schema = 1;**
sqlite> **UPDATE SQLITE_MASTER SET SQL = 'CREATE TABLE BOOKS ( title TEXT NOT
NULL, publication_date TEXT)' WHERE NAME = 'BOOKS';**
sqlite> **PRAGMA writable_schema = 0;**
sqlite> **.q**
Y:\> **sqlite3 booktest**
SQLite version 3.7.4
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> **insert into BOOKS VALUES ("NULLTEST",null);**
sqlite> **.q**
REFERENCES FOLLOW:
pragma writable_schema
When this pragma is on, the SQLITE_MASTER tables in which database can be changed using ordinary UPDATE, INSERT, and DELETE statements. Warning: misuse of this pragma can easily result in a corrupt database file.
[alter table](From http://www.sqlite.org/lang_altertable.html)
SQLite supports a limited subset of ALTER TABLE. The ALTER TABLE command in SQLite allows the user to rename a table or to add a new column to an existing table. It is not possible to rename a column, remove a column, or add or remove constraints from a table.

SQLite supports a limited subset of ALTER TABLE. The ALTER TABLE command in SQLite allows the user to rename a table or to add a new column to an existing table. It is not possible to rename a column, remove a column, or add or remove constraints from a table. But you can alter table column datatype or other property by the following steps.
BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(a,b);
INSERT INTO t1_backup SELECT a,b FROM t1;
DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT
For more detail you can refer the link.

CREATE TABLE temp_Table(x,y[,etc]);
INSERT INTO temp_Table SELECT * FROM Table;
DROP TABLE Table;
ALTER TABLE temp_Table RENAME TO Table;
Thanks for helping me to find a definitive method!

ALTER COLUMN does not exist in SQLite.
Only Supported alter operations:
Alter Table Name
Alter Table Column Name
Add New Column
Drop Column
Alex Jasmin's answer shows possible way
Reference:
Sqlite Alter Table

SQLite Check if Table is FTS4

I'm developing an Android app that uses a SQLite database with FTS4 tables.
In the app there's an option to import a database from the external memory. This database needs to be checked to confirm that it has all the correct tables and columns. I already have the code to do that however I don't know how to check if the tables are "normal" or FTS4. This will result in problems later on with queries with MATCH on them.
The only way I can think of to check if the tables are FTS4 is to do a random query with MATCH and if it gets an error it's because they are not.
Is there a better way to do this like with just a command?

Using MATCH on a plain table results in an error message only if the table has at least one row.
FTS table have a virtual column with the same name as the table name. So you could try a query like SELECT MyTable FROM MyTable.
You could check whether the shadow tables (MyTable_content, MyTable_segdir, etc.) exist.
You could check the CREATE TABLE statement in the system table: SELECT sql FROM sqlite_master WHERE type = 'table' AND name = 'MyTable';

Add unique column to already exist sqlite table

I use SQLite database in Android app, and i want to know how to add a unique column to already created table.
by this i mean that the exist table uniqness determine by 2 values and i want to edit the table uniqueness to be determined by 3 values (the 2 exist and 1 more).
is it possible?

The writable_schema trick does not work for UNIQUE because the internal index would need to be changed.
The only way to make this change is with a temporary copy of the table:
CREATE TABLE NewTable(
[...],
UNIQUE(Col1, Col2, Col3)
);
INSERT INTO NewTable SELECT * FROM MyTable;
DROP TABLE MyTable;
ALTER TABLE NewTable RENAME TO MyTable;
(This should be wrapped in a transaction; Android's onUpdate does this automatically.)

"SQLiteException error: No such table" if I change the table's name in the same DB and run again the app [duplicate]

This question already has answers here:
"No Such Table" Error found in SQLite Android
(11 answers)
Closed 8 years ago.
I have created a fts database DATABASE_NAME and a table FTS_VIRTUAL_TABLE.
I can insert and select values.
If I change the name of the table in my code e.g. FTS_VIRTUAL_TABLE_NEW keeping the same database DATABASE_NAME and run the application I get a SQLiteException error: No such table: FTS_VIRTUAL_TABLE_NEW. I wonder, why, since in onCreate method the proper SQL statement exists. Shouldn't the FTS_VIRTUAL_TABLE_NEW have been created?
However if I change not only the name of the table but also the name of the database (i.e. new database) everything works. The app runs normally (of course with no values in the database initially).
I don't understand why I can't only change the name of the table keeping the same database.

If you change your database schema at all, you need to increment your database version used in your SQLiteOpenHelper constructor and handle upgrades (i.e. drop and recreate or modify tables) in the onUpgrade method.

SQliteException:no such table [duplicate]

I have created one Member_Master table whose primary key is member_id in sqlite manager for android and creating foreign key in child table e.g Event_Master for member_id from Member_Master. I was getting no such table found:Member_Master error
But now I am getting the following error :
SQLiteManager: CREATE TABLE "main"."Events_Master" ("event_id" NUMERIC PRIMARY KEY NOT
NULL ,"event_name" TEXT NOT NULL ,"event_details" TEXT NOT NULL ,"event_start_date"
DATETIME NOT NULL ,"event_end_date" DATETIME NOT NULL ,"event_time" DATETIME NOT NULL
,"event_venue" TEXT NOT NULL ,"min_level" NUMERIC,"status_id" NUMERIC,"member_id"
NUMERIC, foriegn key(member_id) references Member_Master(member_id)ON DELETE CASCADE ON
UPDATE CASCADE) [ near "member_id": syntax error ]
Exception Name: NS_ERROR_FAILURE
Exception Message: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE)
[mozIStorageConnection.createStatement]
Please give me the solution. Since Member_Master table is already created and field name is member_id only.

If you are getting no such table exception, the reason for this is that the table is not created.There can be few reasons like
1 ) The command you have used to create the table is is wrong (and could be a typing error also).
2 ) You are adding a table in an already existing database
When Database is created with specific number of tables you can not add more tables to it .
If you want to add more tables, you need to uninstall the application from your emulator and install the application again only then it shall create the new tables by re creating the database.
Or upgrade the database version , it shall drop all the tables once and then recreate the database.

Try uninstalling the app and reinstall it again. it works most of the times.

If you are getting no such table exception, then It is sure that the tables are not getting created.Have You written create Table query in your DatabaseAdapter class or simply adding a table from SqliteManager.
If you are creating tables dynamically, please write CREATE TABLE query and execute Query.