Modify a Column's Type in sqlite3

Question

I'm pretty new to SQLite 3 and just now I had to add a column to an existing table I had. I went about doing that by doing: ALTER TABLE thetable ADD COLUMN category;.

Of course, I forgot to specify that column's type. The first thing I was thinking about doing was dropping that column and then re-adding it. However, it seems that SQLite does not have a simple way of doing this, and I would have had to backup the table and re-create it without the column.

This seems messy, and I was wondering if there were just a way of modifying/adding a column's type. I would imagine so, but my searching around yielded no results, being new to SQLite, I imagine it was due to my wording being off in the query.

Answer 1

If you prefer a GUI, DB Browser for SQLite will do this with a few clicks.

1. "File" - "Open Database"
2. In the "Database Structure" tab, click on the table content (not table name), then "Edit" menu, "Modify table", and now you can change the data type of any column with a drop down menu. I changed a 'text' field to 'numeric' in order to retrieve data in a number range.

DB Browser for SQLite is open source and free. For Linux it is available from the repository.

Answer 2

SQLite doesn't support removing or modifying columns, apparently. But do remember that column data types aren't rigid in SQLite, either.

See also:

• SQLite Modify Column

Answer 3

It is possible by recreating table.Its work for me please follow following step:

1. create temporary table using as select * from your table
2. drop your table, create your table using modify column type
3. now insert records from temp table to your newly created table
4. drop temporary table

do all above steps in worker thread to reduce load on uithread

Answer 4

It is possible by dumping, editing and reimporting the table.

This script will do it for you (Adapt the values at the start of the script to your needs):

#!/bin/bash

DB=/tmp/synapse/homeserver.db
TABLE="public_room_list_stream"
FIELD=visibility
OLD="BOOLEAN NOT NULL"
NEW="INTEGER NOT NULL"
TMP=/tmp/sqlite_$TABLE.sql

echo "### create dump"
echo ".dump '$TABLE'" | sqlite3 "$DB" >$TMP

echo "### editing the create statement"
sed -i "s|$FIELD $OLD|$FIELD $NEW|g" $TMP

read -rsp $'Press any key to continue deleting and recreating the table $TABLE ...\n' -n1 key 

echo "### rename the original to '$TABLE"_backup"'"
sqlite3 "$DB" "PRAGMA busy_timeout=20000; ALTER TABLE '$TABLE' RENAME TO '$TABLE"_backup"'"

echo "### delete the old indexes"
for idx in $(echo "SELECT name FROM sqlite_master WHERE type == 'index' AND tbl_name LIKE '$TABLE""%';" | sqlite3 $DB); do
  echo "DROP INDEX '$idx';" | sqlite3 $DB
done

echo "### reinserting the edited table"
cat $TMP | sqlite3 $DB