I have a question regarding ORACLE, I wrote a PLSQL CODE that checks if a table exists, if it exists then I select something from this table..pseudocode is like:
if (table exists)
Select from table where....
the problem is that I always get an error if the table does not exist, even if the if condition is never met and the select statement is never executed.
I think it is because my code is checked at compile time: "select from.." and then it prints an error if the table does not exist. How can I solve such an issue?.. here is how my code looks like (I used generic names):
DECLARE
v_table_exists NUMBER;
BEGIN
SELECT NVL(MAX(1), 0)
INTO v_table_exists
FROM ALL_TABLES
WHERE TABLE_NAME = 'TABLE_TEST';
IF v_table_exists = 1 THEN
INSERT INTO MY_TABLE(COLUMN1, COLUMN2, COLUMN3, COLUMN4)
SELECT 1234,
5678,
T.COLUMN_TEST1,
T.COLUMN_TEST2
FROM TABLE_TEST T
WHERE T.FLAG = 1;
END IF;
END;
The issue is exactly in the fact that your procedure con not be compiled as it refers to a non existing object; you may need some dynamic SQL for this; for example:
create or replace procedure checkTable is
vCheckExists number;
vNum number;
begin
-- check if the table exists
select count(1)
into vCheckExists
from user_tables
where table_name = 'NON_EXISTING_TABLE';
--
if vCheckExists = 1 then
-- query the table with dynamic SQL
execute immediate 'select count(1) from NON_EXISTING_TABLE'
into vNum;
else
vNum := -1;
end if;
dbms_output.put_line(vNum);
end;
The procedure compiles even if the table does not exist; if you call it now, you get:
SQL> select count(1) from NON_EXISTING_TABLE;
select count(1) from NON_EXISTING_TABLE
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL> exec checkTable;
-1
PL/SQL procedure successfully completed.
Then, if you create the table and call the procedure again:
SQL> create table NON_EXISTING_TABLE(a) as select 1 from dual;
Table created.
SQL> exec checkTable;
1
PL/SQL procedure successfully completed.
The same way I showed a SELECT, you can do an UPDATE or whatever SQL query you need; if you do something different from a SELECT, the INTO clause has to be removed.
For example, say you need to insert into a different table, the above code should be edited this way:
if vCheckExists = 1 then
execute immediate 'insert into target(a, b, c) select a, 1, 100 from NON_EXISTING_TABLE';
end if;
Everything will need to be done in Dynamic SQL (DBMS_SQL) or EXECUTE_IMMEDIATE otherwise your code will never compile (or package will be invalided) if table does not exists.
DBMS_SQL Example
EXECUTE_IMMEDIATE Example
According to this article, in Oracle Database Server static SQL is indeed checked at compile time to ensure referenced objects exist.
So I advise you to use dynamic SQL instead of static SQL, through a varchar for example.
Related
I have to write a stored procedure that starts copying the data from a table 'company' into a staging table 'company_stg' if no records for that date are present in it.
I have the following code :
CREATE OR REPLACE
PACKAGE BODY PKG_TEST AS
PROCEDURE SP_BILLING AS
BEGIN
EXECUTE IMMEDIATE 'SELECT * FROM COMPANY INTO COMPANY_STG
WHERE NOT EXISTS (SELECT * FROM COMPANY_STG WHERE AS_OF_DATE = "2023-02-08")';
END;
END PKG_TEST;
I AM GETTING THE ERROR "SQL COMMAND NOT PROPERLY ENDED"
company * company_stg have as_of_date as a column. rest all are same.
please help me with this
I have also tried
if not exists (SELECT * FROM COMPANY_STG WHERE AS_OF_DATE = "2023-02-08")
then
select from company into company_stg
So many things look bad in that piece of code...
First, why use dynamic SQL execute immediate? It's best to avoid dynamic SQL as much as possible because it leads to runtime errors and requires pretty much instrumentation so that it may be debugged. Generally you use dynamic SQL when you do not know beforehand the name of a table it will operate on, which is not the case for you. You definitely know you have to work with tables COMPANY and COMPANY_STG. Is it not so?
Then, it doesn't look like you have read the manual to see an insert select.
When you insert into a table, it's best to give the list of columns into which you actually insert data. If one alters that table and adds one or more than one column, the insert which does not have the list of columns will crash.
Thus, to insert into COMPANY_STG data from COMPANY, the SQL should look like below:
insert into company_stg(
... ---- here should be the list of columns you insert data into
)
select
... --- here should the source columns you are willing to insert
from company c
where not exists (
select 1
from company_stg cs
where cs.as_of_date= --- what is the condition??? I did not understand
)
;
You have not given the structures for those tables, so that I can't give you the columns to select and to insert into. Nor did I really understand what the condition for inserting data should be.
SELECT does not perform a copy and SELECT * FROM COMPANY INTO COMPANY_STG is not valid syntax. You want to use an INSERT statement to do that (and check if there is any row first):
CREATE OR REPLACE PACKAGE BODY PKG_TEST AS
PROCEDURE SP_BILLING
AS
BEGIN
DECLARE
v_staged_count NUMBER;
BEGIN
SELECT 1
INTO v_staged_count
FROM COMPANY_STG
WHERE AS_OF_DATE = DATE '2023-02-08'
FETCH FIRST ROW ONLY; -- We don't care how many rows so stop after finding
-- the first one.
-- Stop as rows have been found.
RETURN;
EXCEPTION
WHEN NO_DATA_FOUND THEN
-- Continue
NULL;
END;
INSERT INTO company_stg
SELECT *
FROM COMPANY;
END;
END PKG_TEST;
/
fiddle
On an Oracle 19c DB I need to sample on customers whilst keeping a uniorm distribution to model the moving of customers.
There are (on purpose) multiple rows with the same customers but changeing adderssses to model moving. Thus, for the sampling i need to group first.
Now what I got is that for the SAMPLE clause the source has to be materialized. So in the PL/SQL script I generate a temporary table that i want to use afterwards with SAMPLE.
But even a simple SELECT INTO afterwards doens't work.
set SERVEROUT on;
DECLARE
v_cust_name VARCHAR2(100);
cmd_creation VARCHAR2(500):='CREATE PRIVATE TEMPORARY TABLE ORA$PTT_temp_cust AS(
SELECT cust_id, MIN(name) as name
FROM customers
GROUP BY cust_id)';
BEGIN
EXECUTE IMMEDIATE cmd_creation;
dbms_output.put_line('temp created');
SELECT name
INTO v_cust_name
FROM (SELECT *
FROM ORA$PTT_temp_cust SAMPLE(5))
WHERE ROWNUM =1;
EXECUTE IMMEDIATE 'DROP TABLE ORA$PTT_temp_cust';
dbms_output.put_line('temp dropped');
END;
What I get is this
ORA-06550: line 15, column 18:
PL/SQL: ORA-00942: table or view does not exist
The table gets created. That far I got when I only executed the String for the creation and nothing else. Then I can access the table in a desired script from a different point.
Does this have to do with the compiling? Is there some different way to solve this?
Your PL/SQL Block simple does not compile as the table you query does not exists at the time of compilation.
You must perform event the query with execute immediate
Simplified Example
DECLARE
v_cust_name VARCHAR2(100);
cmd_creation VARCHAR2(500):='CREATE PRIVATE TEMPORARY TABLE ORA$PTT_temp_cust AS select * from dual';
BEGIN
EXECUTE IMMEDIATE cmd_creation;
dbms_output.put_line('temp created');
EXECUTE IMMEDIATE 'SELECT DUMMY FROM ORA$PTT_temp_cust' INTO v_cust_name;
dbms_output.put_line('name' || v_cust_name);
EXECUTE IMMEDIATE 'DROP TABLE ORA$PTT_temp_cust';
dbms_output.put_line('temp dropped');
END;
/
An other caveat the can lead to ORA-00942: table or view does not existin your setup is that you performs commit in your script.
The default definition of the ON COMMIT clause is DROP DEFINITION so you must use
CREATE PRIVATE TEMPORARY TABLE ORA$PTT_temp_cust
ON COMMIT PRESERVE DEFINITION
...
Dynamic SQL is evil. The fact that you created the table using dynamic SQL (your 1st execute immediate) doesn't mean that Oracle "predicts" you'll actually succeed with that and "presume" that statements that follow are correct. Nope - that table doesn't exist yet, so everything has to be moved to dynamic SQL.
Something like this (disregard changes in table and column names I used and global vs. private temporary table; this is 11gXE):
SQL> DECLARE
2 v_cust_name VARCHAR2 (100);
3 cmd_creation VARCHAR2 (500)
4 := 'CREATE global TEMPORARY TABLE PTT_temp_cust AS
5 SELECT empno, MIN(ename) as name
6 FROM emp
7 GROUP BY empno';
8 BEGIN
9 EXECUTE IMMEDIATE cmd_creation;
10
11 EXECUTE IMMEDIATE '
12 SELECT max(name)
13 FROM (SELECT *
14 FROM PTT_temp_cust SAMPLE(5))
15 WHERE ROWNUM = 1'
16 INTO v_cust_name;
17
18 EXECUTE IMMEDIATE 'DROP TABLE PTT_temp_cust';
19
20 DBMS_OUTPUT.put_line ('Result = ' || v_cust_name);
21 END;
22 /
Result =
PL/SQL procedure successfully completed.
SQL>
I got no result, though - but you should (at least, I hope so).
I have a created a procedure as
create or replace procedure availability(num in number) as
begin
delete from vehicle_count;
insert into vehicle_count from select engine_no,count(engine_no)
from vehicle
where engine_no = num
group by engine_no;
end;
/
The procedure was created successfully but now i have to write a separate query to view the contents of vehicle_count as
select * from vehicle_count;
I tried inserting the select statement into the procedure after insertion but it showed a error stating "an INTO clause is expected in the select statement".
How can I create procedure to select the required contents and display it in a single execute statement?
Table schema
vehicle(vehicle_no,engine_no,offence_count,license_status,owner_id);
vehicle_count(engine_no,engine_count);
Check this (MS SQL SERVER)-
create or alter procedure availability(#num as int) as
begin
delete from vehicle_count;
insert into vehicle_count
output inserted.engine_no,inserted.count_engine_no
select engine_no,count(engine_no) as count_engine_no
from vehicle
where engine_no=#num
group by engine_no;
end;
If you want to use a SELECT into a PL/SQL block you should use either a SELECT INTO or a loop (if you want to print more rows).
You could use something like this:
BEGIN
SELECT engine_no, engine_count
INTO v_engine, v_count
FROM vehicle_count
WHERE engine_no = num;
EXCEPTION
WHEN NO_DATA_FOUND THEN
v_engine := NULL;
v_count := NULL;
END;
v_engine and v_count are two variables. You can declare them in your procedure, and they will contain the values you want to print.
You said that the procedure you wrote (actually, you posted here) compiled successfully. Well, sorry to inform you - that's not true. This is not a valid syntax:
insert into vehicle_count from select engine_no,count(engine_no)
----
from? Here?
Consider posting true information.
As of your question (if we suppose that that INSERT actually inserted something into a table):
at the beginning, you delete everything from the table
as SELECT counts number of rows that share the same ENGINE_NO (which is equal to the parameter NUM value), INSERT inserts none (if there's no such NUM value in the table) or maximum 1 row (because of aggregation)
therefore, if you want to display what's in the table, all you need is a single SELECT ... INTO statement whose result is displayed with a simple DBMS_OUTPUT.PUT_LINE which will be OK if you're doing it interactively (in SQL*Plus, SQL Developer, TOAD and smilar tools). Regarding table description, I'd say that ENGINE_NO should be a primary key (i.e. that not more than a single row with that ENGINE_NO value can exist in a table).
create or replace procedure availability (num in number) as
l_engine_no vehicle_count.engine_no%type;
l_engine_count vehicle_count.engine_count%type;
begin
delete from vehicle_count;
insert into vehicle_count (engine_no, engine_count)
select engine_no, count(engine_no)
from vehicle
where engine_no = num
group by engine_no;
-- This query shouldn't return TOO-MANY-ROWS if ENGINE_NO is a primary key.
-- However, it might return NO-DATA-FOUND if there's no such NUM there, so you should handle it
select engine_no, engine_count
into l_engine_no, l_engine_count
from vehicle_count
where engine_no = num;
dbms_output.put_line(l_engine_no ||': '|| l_engine_count);
exception
when no_data_found then
dbms_output.put_line('Nothing found for ENGINE_NO = ' || num);
end;
/
There are numerous alternatives to that (people who posted their answers/comments before this one mentioned some of those), and the final result you'd be satisfied with depends on where you want to display that information.
All i want is to select all rows from a table and once it is selected and displayed, the data residing in table must get completely deleted. The main concern is that this must be done using sql only and not plsql. Is there a way we can do this inside a package and call that package in a select statement? Please enlighten me here.
Dummy Table is as follows:
ID NAME SALARY DEPT
==================================
1 Sam 50000 HR
2 Max 45000 SALES
3 Lex 51000 HR
4 Nate 66000 DEV
Any help would be greatly appreciated.
select * from Table_Name;
Delete from Table_Name
To select the data from a SQL query try using a pipelined function.
The function can define a cursor for the data you want (or all the data in the table), loop through the cursor piping each row as it goes.
When the cursor loop ends, i.e. all data has been consumed by your query, the function can perform a TRUNCATE table.
To select from the function use the following syntax;
SELECT *
FROM TABLE(my_function)
See the following Oracle documentation for information pipelined functions - https://docs.oracle.com/cd/B28359_01/appdev.111/b28425/pipe_paral_tbl.htm
This cannot be done inside a package, because " this must be done using sql only and not plsql". A package is PL/SQL.
However it is very simple. You want two things: select the table data and delete it. Two things, two commands.
select * from mytable;
truncate mytable;
(You could replace truncate mytable; with delete from mytable;, but this is slower and needs to be followed by commit; to confirm the deletion and end the transaction.)
Without pl/sql it's not possible.
Using pl/sql you can create a function which will populate a row, and then delete
Here is example :
drop table tempdate;
create table tempdate as
select '1' id from dual
UNION
select '2' id from dual
CREATE TYPE t_tf_row AS OBJECT (
id NUMBER
);
CREATE TYPE t_tf_tab IS TABLE OF t_tf_row;
CREATE OR REPLACE FUNCTION get_tab_tf RETURN t_tf_tab PIPELINED AS
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
FOR rec in (select * from tempdate) LOOP
PIPE ROW(t_tf_row(rec.id));
END LOOP;
delete from tempdate ; commit;
END;
select * from table(get_tab_tf) -- it will populate and then delete
select * from tempdate --you can check here result of deleting
you can use below query
select * from Table_demo delete from Table_demo
The feature you seek is SERIALIZABLE ISOLATION LEVEL. This feature enables repeatable reads, which in particular guarantee that both SELECTand DELETEwill read and process the same identical data.
Example
Alter session set isolation_level=serializable;
select * from tempdate;
--- now insert from other session a new record
delete from tempdate ;
commit;
-- re-query the table old records are deleted, new recor preserved.
I have a table that store the name of other tables. Like
COL_TAB
--------------
TABLE_NAME
--------------
TAB1
TAB2
TAB3
What i want to do is that, i want to run a sql query on table like this,
SELECT * FROM (SELECT TABLE_NAME from COL_TAB WHERE TABLE_NAME = 'TAB1')
Thanks
An Oracle SQL query can use a dynamic table name, using Oracle Data Cartridge and the ANY* types. But before you use those advanced features, take a step back and ask yourself if this is really necessary.
Do you really need a SQL statement to be that dynamic? Normally this is better handled by an application that can submit different types of queries. There are many application programming languages and toolkits that can handle unexpected types. If this is for a database-only operation, then normally the results are stored somewhere, in which case PL/SQL and dynamic SQL are much easier.
If you're sure you've got one of those rare cases that needs a totally dynamic SQL statement, you'll need something like my open source project Method4. Download and install it and try the below code.
Schema Setup
create table tab1(a number);
create table tab2(b number);
create table tab3(c number);
insert into tab1 values(10);
insert into tab2 values(20);
insert into tab3 values(30);
create table col_tab(table_name varchar2(30), id number);
insert into col_tab values('TAB1', 1);
insert into col_tab values('TAB1', 2);
insert into col_tab values('TAB1', 3);
commit;
Query
select * from table(method4.dynamic_query(
q'[
select 'select * from '||table_name sql
from col_tab
where id = 1
]'));
Result:
A
--
10
You'll quickly discover that queries within queries are incredibly difficult. There's likely a much easier way to do this, but it may require a design change.
I don't have a database by hand to test this but I think you are looking for something like this:
DECLARE
-- Create a cursor on the table you are looking through.
CURSOR curTable IS
SELECT *
FROM MainTable;
recTable curTable%ROWTYPE;
vcQuery VARCHAR2(100);
BEGIN
-- Loop through all rows of MainTable.
OPEN curTable;
LOOP
FETCH curTable INTO recTable;
EXIT WHEN curTable%NOTFOUND;
-- Set up a dynamic query, with a WHERE example.
vcQuery := 'SELECT ColumnA, ColumnB FROM ' || recTable.Table_Name || ' WHERE 1 = 1';
-- Execute the query.
OPEN :dyn_cur FOR vcQuery;
END LOOP;
CLOSE curTable;
END;
/
Try this
CREATE OR REPLACE PROCEDURE TEST IS
sql_stmt VARCHAR2(200);
V_NAME VARCHAR2(20);
BEGIN
sql_stmt := 'SELECT * FROM ';
EXECUTE IMMEDIATE sql_stmt|| V_NAME;
END;
Update
select statement dont work in procedure.
in sql server you can try sql block
Declare #name varchar2(50)
Select #name='Select * from '+TABLE_NAME from COL_TAB WHERE TABLE_NAME = 'TAB1'
EXEC(#name);