Sqlite: Preventing Duplicate Rows

SQLite: Preventing Duplicate Rows

Declare a unique constraint on (user, location).

CREATE TABLE Permission (
    permissionID integer primary key,
    user integer not null,
    location integer not null,
    unique (user, location)
);

sqlite> insert into Permission (user, location) values (1, 2);
sqlite> insert into Permission (user, location) values (1, 2);
Error: UNIQUE constraint failed: Permission.user, Permission.location

SQLite: Prevent insertion of duplicate rows without failing

You can do it with INSERT OR IGNORE INTO....:

create table tableA(
  col1 int, 
  col2 text unique
);
insert into tableA(col1, col2) values
(1, 'a'), (2, 'b');

create table tableB(
  col1 int, 
  col2 text unique
);
insert into tableB(col1, col2) values
(1, 'a'), (2, 'b'), (3, 'c');

insert or ignore into tableA(col1, col2) 
select col1, col2 
from tableB;

select * from tableA;

See the demo.

Results:

| col1 | col2 |
| ---- | ---- |
| 1    | a    |
| 2    | b    |
| 3    | c    |

How to prevent duplicate rows or data in SQLite with Python?

make a primary key in your table and set on conflict on that constraint like so :

create table if not exists users
( 
  user_id integer primary key not null on conflict ignore 
  , name text 
  , age integer 
  , phone integer
)

and now if that primary key is violated , when you insert or update nothing happens.
also quick tip saving phone number in int datatype is not the best practice , it's takes more memory and you are limited to numbers and etc..

How to avoid duplicate rows in SQLite database in Android?

android.database.sqlite.SQLiteException: near "fromPDF_TABLEwhereNAME": syntax error (code 1 SQLITE_ERROR): , while compiling: Select * fromPDF_TABLEwhereNAME=fhg.pdf

Currently, your sql statement is like this:

Select * fromPDF_TABLEwhereNAME=fhg.pdf

You need to add space. Your sql statement need to be like this:

Select * from PDF_TABLE where NAME = fhg.pdf

In DocumentsFragment.java, try changing the code from

Cursor cursor=MyDbHandler.database.rawQuery("Select * from" + Params.TABLE_NAME + "where"+Params.KEY_NAME+ "=" +(pdf.get(position).getName()) ,null);

To

Cursor cursor=MyDbHandler.database.rawQuery("Select * from " + Params.TABLE_NAME + " where "+Params.KEY_NAME+ " = " +(pdf.get(position).getName()) ,null);

How to avoid inserting duplicate data when inserting data into SQLite3 database using python?

It depends on how much constraint you want to put on "avoiding duplicates".
Strictly speaking, you can avoid any duplicates by add constraints to your table:

CREATE TABLE MAIN
   (
   NAME           TEXT    NOT NULL,
   Error_List          CHAR(50),
   Warning_List        CHAR(50),
   Advice_List         CHAR(50),
   Total          CHAR(50),
   Note           CHAR(50),
UNIQUE (NAME, Error_List, Warning_List, Advice_List, Total, Note) ON CONFLICT IGNORE
);

In this example I used a "table constraint", when the constraint spans multiple columns. You can also use a "column constraint" if you want to avoid a single value being duplicated.
For both cases, you can alter the conflict response, either IGNORE, REPLACE, ABORT, etc., depending on which behaviour you wish to elicit. These conflicts responses can also be set in the INSERT statements as,

INSERT OR REPLACE INTO MAIN (...) VALUES (...)

https://sqlite.org/lang.html

SQLite: prevent duplicates

You can use the column constraint UNIQUE.

The UNIQUE constraint causes an unique index to be created on the specified columns.

SQLite3 - Preventing duplicate entries from being entered into a database

Let the database do the work. Create a unique index. This will prevent such duplication:

create unique index unq_notify_users_2 on notify_users(language_code, username);

It prevents duplication by generating an error. Although it is best to do the check in the database, you can avoid the error by doing something like this:

insert into notify_users(language_code, username)
    select language_code, username
    from (select $language_code as language_code, $username as username) lu
    where not exists (select 1
                      from notify_users nu
                      where nu.language_code = lu.language_code and
                            nu.username = lu.username
                     );

SQLite INSERT OR IGNORE doesn't ignore duplicates

INSERT OR IGNORE works only when there are unique constraints in the table.

Since there aren't and you can't add any, because SQLite is not that flexible, the only way to do what you want is like this:

INSERT or IGNORE INTO dest.AnalogInput 
SELECT * FROM AnalogInput WHERE ....
EXCEPT
SELECT * FROM dest.AnalogInput

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