If I alter the table and add a new column will add the data be wiped off from that table.
ALTER TABLE MyTable ADD COLUMN noOfDays integer default 0 NOT NULL
Will the above SQL command drop MyTable and then ALTER it with the noOfDays column or will it simply add the noOfDays column without dropping it.
No, add just adds the column. Neither its data will be deleted nor the table be dropped.
p.s. from the documentation
"Note: also that when adding a CHECK constraint, the CHECK constraint is not tested against preexisting rows of the table." (check SQLite manual for more)
Related
I have two SQLite files, each of them has one table and the same table design. One Column is set as Primary Key. I want to copy all data from ItemsB into ItemsA. All data should be updated. The ItemsB Table is the newer one.
I've tried:
ATTACH DATABASE ItemsB AS ItemsB;
INSERT INTO ItemsA.PMItem (ItemID,VarID,Name1) SELECT ItemID,VarID,Name1 FROM ItemsB.PMItem;
Obviously this can't work due the Primary Key (which is the column VarID).
Then I tried it with ON CONFLICT:
ON CONFLICT (VarID) DO UPDATE SET Name1=excluded.Name1
But this won't work either.
Example Table:
CREATE TABLE PMItem (
ItemID INTEGER,
VarID INTEGER PRIMARY KEY,
Name1 TEXT
);
You need a WHERE clause with an always true condition, to overcome the ambiguity that is raised when ON CONFLICT is used after a SELECT statement:
INSERT INTO PMItem (ItemID,VarID,Name1)
SELECT ItemID,VarID,Name1
FROM ItemsB.PMItem
WHERE 1
ON CONFLICT(VarID) DO UPDATE
SET Name1 = EXCLUDED.Name1;
Before adding (ALTER) new column to table I want to check if that table exists. Because app is crashing since table is not present and we tried to add column to it.
I tried "Alter table if exist table_name add column abc" but no luck.
I want to do this in 1 query.
Is it possible to delete a column from an SQLlite database. I have Googled this and it seems to be impossible.
From the ALTER TABLE manual;
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.
So, no, not without dropping and recreating the table.
According to the docs:
It is not possible to rename a column, remove a column, or add or
remove constraints from a table.
I guess it has to be done manually.
Hi In my application I am using SQLITE database,
I want to add multiple column in table,
If i am adding one column that work fine,
I am using ALTER table for add new column,
With this i am able to update one column,
ALTER TABLE "main"."tblCredit" ADD COLUMN "CardDetail" VARCHAR
But How can i add multiple column in tblCredit table.
Use repeated calls to ALTER TABLE.
You should not have to do this too often anyway.
IN DB2
with the help of alter command add multiple column in table
ALTER TABLE TABLE_NAME ADD COLUMN F_NAME VARCHAR(30)
ADD COLUMN L_NAME VARCHAR(30)
ADD COLUMN ROLL_NO INTEGER
ADD COLUMN MOBILE_NUMBER VARCHAR(12);
How do I change the default value of an existing column in a table in sqlite3?
I have a table named notes with a boolean column named hidden. The default is set to true, I want to set it to false.
I don't think you can without replacing the whole table. From the fine manual:
SQL Features That SQLite Does Not Implement
Complete ALTER TABLE support
Only the RENAME TABLE and ADD 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.
So there is no way to modify an existing column in SQLite. I think you'll have to create a new table with the appropriate default for hidden, copy all the data over, drop the original notes table, and then rename the new one.
SQLite stays lean by purposefully omitting a lot of features.
SQLite database browser allows you to drop columns, so you could drop the column with it, and then manually add the column with the default using the sqlite3 command line tool.
Create a new database with the same schema (but your new default value), attach both, and migrate.
For deleting columns or other changes that aren't supported by the "ALTER TABLE" syntax, I create a new table, migrate date into it, drop the old table, and rename the new table to the original name.
https://stackoverflow.com/a/998652/1020467
https://www.sqlite.org/lang_altertable.html