I am using SQLite for my application. when I used truncate command in SQLite it gives me error like " syntax Error near truncate".
Can anyone help me to solve this problem or any other alternative of truncate except DELETE command.
Why not DELETE?
DELETE with an empty WHERE clause should be pretty fast in SQLite because it does sth called "truncate optimization", see
http://www.sqlite.org/lang_delete.html
SQLite DELETE FROM is not equivalent to T-SQL TRUNCATE TABLE.
SQLite DELETE FROM will not reset the index in a field marked autoincrement.
The SQLLite Delete Truncation Optimization DELETE FROM {table}; (with no WHERE clause) has similar behaviour to the SQL Server TRUNCATE TABLE {table};. See the SQLLite documentation here
The Truncate Optimization
When the WHERE is omitted from a DELETE statement and the table being deleted has no triggers, SQLite uses an optimization to erase the entire table content without having to visit each row of the table individually. This "truncate" optimization makes the delete run much faster. Prior to SQLite version 3.6.5 (2008-11-12), the truncate optimization also meant that the sqlite3_changes() and sqlite3_total_changes() interfaces and the count_changes pragma will not actually return the number of deleted rows. That problem has been fixed as of version 3.6.5 (2008-11-12).
The truncate optimization can be permanently disabled for all queries by recompiling SQLite with the SQLITE_OMIT_TRUNCATE_OPTIMIZATION compile-time switch.
There is none.
Just use DELETE without any arguments.
This is how it is implemented by Drupal 7's database abstraction layer:
http://api.drupal.org/api/drupal/includes--database--sqlite--query.inc/function/TruncateQuery_sqlite%3A%3A__toString/7
Related
I have defined this mapper method:
#Delete("truncate table MY_TABLE")
public void wipeAllData();
and it usually works...anyway sometimes it doesn't...is there any particular reason/known bug for that?
I'm using mybatis 3.3.0 with oracle 11g as DBMS.
EDIT
Since you added the oracle11g tag. My previous answer is no longer valid, at least not the reason why it would not be working. So I edited it.
There are some reasons that I'm aware of why sometimes it is not working in ORACLE. According to the ORACLE docs
You cannot individually truncate a table that is part of a cluster. You must either truncate the cluster, delete all rows from the table, or drop and re-create the table.
You cannot truncate the parent table of an enabled foreign key constraint. You must disable the constraint before truncating the table. An exception is that you can truncate the table if the integrity constraint is self-referential.
You cannot truncate the parent table of a reference-partitioned table. You must first drop the reference-partitioned child table.
But you should be aware that the usage or a TRUNCATE command is not ideal in an application scope. It should be an operation executed on the database only. The reason lies in another indication of the docs:
If table is not empty, then the database marks UNUSABLE all nonpartitioned indexes and all partitions of global partitioned indexes on the table. However, when the table is truncated, the index is also truncated, and a new high water mark is calculated for the index segment. This operation is equivalent to creating a new segment for the index. Therefore, at the end of the truncate operation, the indexes are once again USABLE.
So it can be a painfully long operation depending on indexes and the size of the table.
Also, for tables that have constraints the truncate operation will not drop the table, it will delete registries one by one. If you have ON DELETE CASCADE on your constraints, if not, an error will be thrown. This is still true for oracle database
Another thing will should aware of is
Removing rows with the TRUNCATE TABLE statement can be faster than removing all rows with the DELETE statement, especially if the table has numerous triggers, indexes, and other dependencies.
So if by any means you have a trigger on that table it will do nothing.
The original DOC about TRUNCATE command is here:
TRUNCATE TABLE
I have always used a custom implementation of SQLite, and it had the "LATIN_NOCASE" collation.
I am now using System.Data.SQLite, and it doesn't have this collation, as I have found out now.
I would therefore like to change all indexes from LATIN_NOCASE to NOCASE.
Can I somehow do that with one line of code, or do I have to recreate the table / the indexes?
SQLite is designed as a lightweight, embedded database where large changes to the database are not supposed to happen at runtime, so it has no ALTER INDEX command: http://www.sqlite.org/lang.html.
delete N.* from Tbl_Nodes N, Data_Tree DT WHERE N.Part = DT.Part
for this command I am getting following error.
System.Data.SQLite.SQLiteException: SQLite error near "N": syntax error
Above command works fine for MSAccess.
Is there any alternative to use table shortcut in Sqlite?
The DELETE statement operates on a single table and does not use a table alias. Therefore, your FROM clause must read FROM Tbl_Nodes.
You're probably looking for:
delete from Tbl_Nodes WHERE Part IN (SELECT Part FROM Data_Tree)
Note that this will remove all nodes from Tbl_Nodes that have a corresponding Part value in Data_Tree but does not remove any records from Data_Tree itself.
While SQL varies somewhat among vendors, as a general principle it's a mistake to learn SQL from MS Access and try to apply it to other products. MS Access features some very non-standard constructions.
Using an alias for the table?
FROM table AS t1
You're missing a bit of your SQL statement there I guess but does it not work if you just say:
delete N from Tbl_Nodes N, Data_tree DT WHERE...(rest of statement)
I've just removed the .*
I have a .sqlite db which contains only one table. That table contains three columns and I am interested in indexing one column ONLY.
The problem is, when I perform the indexing, I got an empty index table !
I am using SQLite Manager add-ons for Firefox. This is the syntax that appears before I confirm the indexing:
CREATE INDEX "main"."tableIndex" ON "table" ("column1" ASC)
I don't know what is the problem here. I tried this tool - long time ago - with another database and it works fine.
Any suggestion ?
You cannot "see" the contents of a database index. No table or table-like structure is created that corresponds to the index. So there is nothing to look at that could be empty.
If the CREATE INDEX command ran without error, you can be confident that the index was created and will continue to be maintained by SQLite as you add, remove, and update data.
As per the comments, below, #iturki is actually trying to index for full text search. SQLite supports several extensions for full text search but they are not implemented through the stanard CREATE INDEX command. See this reference.
Try use VACUUM query. It will completely rebuild sqlite database file and will rebuild all indices and reset all ROWID etc.
I want a debug function to do this, but I'm unaware of whether one already exists. Going through and using 'drop table' for each of my tables will be a pain.
Help appreciated.
Since the database is just one file, you can indeed just erase it. If you want something more automatic, you can use the following to do it all programmatically:
Recover your schema:
SELECT group_concat(sql,';') FROM sqlite_master;
Disconnect from the database
Delete the database file
Create your schema again with what was returned from the above query
If you used any particular options for your original database (page_size, etc), they will have to be declared manually as well.
to "drop database" for sqlite, simply delete the database file (and recreate if needed)