I am developing a Iphone App.
I need to know whether we can execute multiple insert statements in a batch at once using sqlite3 database.
As we do this in Core java in JDBC bt using execute_batch can we do the same using sqlite3 database?Can any one guide me how can i do this using sqlite3 by providing any code or link?
Thanks,
Shradha
You can do it by performing next queries:
BEGIN;
INSERT ....;
INSERT ....;
INSERT ....;
INSERT ....;
COMMIT;
Be careful with TCL, sqlite3 won't perform any DML and DDL till transaction will be COMMIT.
With using statements you won't be able to perform few commands at once if they separated by ';', statement prepare have pointer at which it will place commands which won't be performed int this statement.
We can pass multiple statements separated by a semicolon.
Example: "delete from table1;delete from table2;" This will delete the contents of table1 and table2. Similarly we can create insert statements.
Related
I am unsure which activity I need to run commands to update, delete or add to a datatable in SQLite from UIPath. Which activities do I use?
If you want to update, insert or delete single records, you will use a Execute non-query activity
It is very similar to the query one except it doesn’t produce a table as output. The output will be “Affected Records” which is an integer variable.
The query string will be pure SQL
I would like to load text from a field in a SQLite table and run it as a SQLite query. All done in a SQLite query. No external string operations, nor command line operations are possible. Pure SQLite only.
Let's say that I would create a table command_table with the rows:
COMMAND_NAME: COMMAND:
command1 SELECT * FROM table1
command2 SELECT * FROM table1 WHERE table1.row1 = '1'
The desired SQLite command would be able to load the COMMAND and interpret it.
The commands would be as complex as it gets, so using some generic comparisons like WHERE table1.row1 = command_table.command1" is not an option.
SQLite is designed as an embedded database, i.e., to be used together with a 'real' programming language. Therefore, it does not have any mechanism to execute dynamic SQL statements from within SQL itself.
I want to create a new table for every row that is inserted into an existing table.
As I understand only DML operation is allowed on trigger, is it correct.
If so is there a alternative way of achieving my objective?
SQLite indeed allows only DML in a trigger body.
However, you could do a SELECT with a user-defined function that then executes another SQL command to create the table:
CREATE TRIGGER ...
...
BEGIN
SELECT my_create_table_function(NEW.name);
END;
Why do we use "Execute immediate" in plsql? I know we use it to execute dynamic sql statements. But still I'm unable to convince interviewer. Could anybody give me an exact and proper answer for this? Though I use it everyday, but still unable to explain it. One thing I know is, it's used in DML statements and to retrieve multiple rows through select statement. Please give an exact definition for using "Execute immediate".
EXECUTE IMMEDIATE enables execution of a DML or DDL statement which is held as a string and only evaluated at runtime. This enables one to dynamically create the statement based on program logic. EXECUTE IMMEDIATE is also the only way you can execute DDL within a PL/SQL block. See the Oracle Manual for a complete and thorough review of these features.
While this is a very useful facility it should be used with care. Unless there is an explicit need for dynamic sql then it is better to directly declare the sql within your PL/SQL code. This will enable Oracle to parse the SQL at compile time for validity and also reduce overhead when executing the pre-compiled statement. Also you need to be very careful to avoid SQL injection attacks when dynamically building SQL.
For example, let's say you have some kind of application where users define their company and all the work they do. If you want to make it dynamically for users, then you can give them option to create their own models(tables). Since you do not know how many tables they will have, and how many attributes this tables will have you can use execute immediate.
DDL Statement in Procedures or Anonymous PLSQL blocks
Here is an example showing how to use dynamic DDL to create, drop and re-create a table:
BEGIN
EXECUTE IMMEDIATE 'create table abcd (efgh NUMBER)';
EXECUTE IMMEDIATE 'drop table abcd';
EXECUTE IMMEDIATE 'create table abcd (efgh VARCHAR2(10))';
END;
You can use this method to execute any DDL.
Though it's not suggested to use Execute Immediate for DDL, rather Global Temp Table should be used.
To execute DML statements in Procedures or Anonymous PLSQL blocks
To execute DML commands more often than DDL. With dynamic SQL you can issue inserts, updates and deletes just as you can with static SQL:
BEGIN
EXECUTE IMMEDIATE 'INSERT INTO abcd (efgh) VALUES (:text_string)'
USING 'ijkl';
EXECUTE IMMEDIATE 'INSERT INTO abcd (efgh) VALUES (:text_string)'
USING 'mnop';
EXECUTE IMMEDIATE 'UPDATE abcd ' ||
'SET efgh = :text_string WHERE efgh = :second_string'
USING 'qrst', 'mnop';
EXECUTE IMMEDIATE 'DELETE FROM abcd ' ||
'WHERE efgh = :text_string '
USING 'qrst';
END;
In Select queries with bind variables
As useful as DDL and DML are, a database is not very useful if you can't get your data out. You can also use execute immediate to select your data back out.
DECLARE
v_data abcd.efgh%TYPE;
v_data_row abcd%ROWTYPE;
BEGIN
EXECUTE IMMEDIATE 'SELECT efgh FROM abcd WHERE efgh = :text_string'
INTO v_data
USING 'ijkl';
DBMS_OUTPUT.PUT_LINE( 'Column Variable: ' || v_data );
EXECUTE IMMEDIATE 'SELECT * FROM abcd WHERE efgh = :text_string'
INTO v_data_row
USING 'ijkl';
DBMS_OUTPUT.PUT_LINE( 'Row Variable: ' || v_data_row.efgh );
END;
INFO: Column Variable: ijkl
INFO: Row Variable: ijkl
How does one prepare a statement from the SQLite CLI? I have found the page Compiling An SQL Statement but it is geared more towards the ODBC interface, not the CLI interpreter. I'm hopinpg for something akin to the following:
sqlite> pq = prepare(SELECT * FROM Users WHERE username=?)
sqlite> run(pq, 'jeffatwood')
0 | jeffatwood | hunter2 | admin
sqlite>
Does the SQLite CLI have any such functionality? Note that I am not referring to the Bash CLI but rather SQLite's CLI interpreter or the excellent LiteCLI alternative.
Perhaps SQL Parameters using named parameters would do the trick
sqlite> .param set :user 'jeffatwood'
sqlite> select * from Users where username = :user
should return the desired row.
CLI was not designed for such. For this you must use an SQLite API on an available programming language.
You may also write a batch/shell file to handle CLI call.
E.g., in Windows a file named User.bat like following:
#SQLITE3.EXE some.db "SELECT * FROM Users WHERE username='%~1'"
May be called like this:
User "jeffatwood"
will perform desired result.
EDIT:
About prepared/compiled statements: with those you can bind parameters, fetch queries row by row and repeat same command in a faster manner.
sqlite3 CLI tool wouldn't take any advantage on those:
all parameters must be typed in SQL statement, making binding useless;
all query rows are returned at once, no need to fetch row by row;
repeated commands must be retyped - small speed improvement would result in using precompiled statements.