I have two scripts which needs to be executed depending on whether a table exists or not in my database.
So I created a 3rd script as below which checks the condition and calls the respective script.
[Because my installer cannot reach db and it can only call one script while installation]
declare
cnt number;
begin
select count(*)
into cnt
from all_tables where table_name = 'VQ_REPORT_LAUNCHER';
if (cnt>0) then
begin
#VQ_Alter_Script.sql;
end;
else
begin
#VQ_Create_Script.sql;
end;
end if;
END;
I get the below error -
ERROR at line 10:
ORA-06550: line 10, column 1:
PLS-00103: Encountered the symbol "CREATE" when expecting one of the following:
Note - When I execute my create/alter scripts directly from sql plus it works.
Only when I try to execute them through a 3rd script using IF-ELSE , i get the above error in sql plus.
You can use substitution variables to decide which script to run.
column script_name new_value script_name
select case count(*)
when 0 then 'VQ_Create_Script.sql'
else 'VQ_Alter_Script.sql'
end as script_name
from all_tables
where table_name = 'VQ_REPORT_LAUNCHER';
#&script_name
or if only part of the name changes you could do:
column script_type new_value script_type
select case count(*) when 0 then 'Create' else 'Alter' end as script_type
from all_tables
where table_name = 'VQ_REPORT_LAUNCHER';
#VQ_&script_type._Script.sql
You can add settings like set termout off and set termout on around the query part to hide it if you want, and use set verify to decide whether to show the substitution happening.
Depending on which user you run this as, you might want to either check against user_tables rather than all_tables, or include the expected table owner as part of the filter, so you don't accidentally pick up a table with the same name in the wrong schema.
Related
We want to run a simple SQL statement (dropping and creating an index), but only if the old index has not already been deleted. After looking up the syntax for IF in DB2, I came up with this:
IF EXISTS (SELECT indname FROM SYSCAT.INDEXES WHERE INDNAME = 'TEST_CREATE_INDEX_OLD')
THEN
DROP INDEX TEST_CREATE_INDEX_OLD;
create index TEST_CREATE_INDEX_NEW on example_table
(
id,
another_field
);
END IF;
When run with either SQuirrel (already setup to run with db2) or via command line, this script results in an error:
An unexpected token "IF EXISTS (SELECT indname FROM SYSCAT.INDEX" was
found following "BEGIN-OF-STATEMENT". Expected tokens may include:
"".. SQLCODE=-104, SQLSTATE=42601, DRIVER=4.23.42 SQL Code:
-104, SQL State: 42601
So - what am I doing wrong? Am I missing something, or is there another way to achieve my goal (check for $thing in database, execute appropriate query) that so far has not occured to me?
If IF statement is valid only in a compound-SQL block (i.e. inside a stored-procedure/routine/function/anonymous-block).
It's not valid standalone as your question shows, and that is why Db2 throws the -104 error.
You can look up the explanation of the sqlcode -104 by looking up SQL0104N in the free online Db2 Knowledge Center at this link.
To be able to use compound-SQL in your Squirrel-SQL tool, you need to configure squirrel to use an alternative statement terminator. Google that. In the examples below, I show a statement terminator of # (to delimit the block).
Here are two different ways to do what you want with Db2-Linux/Unix/Windows, each uses an anonymous block. Other approaches are possible.
In this example the drop-index will only run if the index-name exists in the current schema:
begin
declare v_index_exists integer default 0;
select 1 into v_index_exists
from syscat.indexes
where indname = 'TEST_CREATE_INDEX_OLD';
if v_index_exists = 1
then
execute immediate('drop index TEST_CREATE_INDEX_OLD');
execute immediate('create index TEST_CREATE_INDEX_NEW on example_table ( id, another_field)');
end if;
end#
In this example the drop-index will always run, but the block won't abort if the index does'nt exist (i.e. it will continue and not throw any error).
begin
declare v_no_such_index integer default 0;
declare not_exists condition for sqlstate '42704';
declare continue handler for not_exists set v_no_such_index=1;
execute immediate('drop index TEST_CREATE_INDEX_OLD');
execute immediate('create index TEST_CREATE_INDEX_NEW on example_table ( id, another_field)');
end#
You must use another statement delimiter, if you want to use db2 compound statement.
In Squirrel: Session -> Session Properties -> SQL -> Statement Separator = #.
Indexes in Db2 are fully qualified by 2 SYSCAT.INDEXES columns: INDSCHEMA and INDNAME. So, it's advisable to use both these fields in a SELECT statement on SYSCAT.INDEXEX as in example.
You can't use static DDL statements in a compound statement. Use EXECUTE IMMEDIATE statements instead.
Below is an example emulating UPDATE INDEX for the index in a schema equal to CURRENT SCHEMA special registry set in the session.
BEGIN
IF EXISTS (SELECT indname FROM SYSCAT.INDEXES WHERE INDSCHEMA = CURRENT SCHEMA AND INDNAME = 'TEST_CREATE_INDEX_OLD')
THEN
EXECUTE IMMEDIATE 'DROP INDEX TEST_CREATE_INDEX_OLD';
EXECUTE IMMEDIATE'
create index TEST_CREATE_INDEX_NEW on example_table
(
id,
another_field
)
';
END IF;
END
#
I have an PostgreSQL query that includes a transaction and an exception if a column is duplicated:
BEGIN;
ALTER TABLE "public"."cars"
ADD COLUMN "top_speed" text;
EXCEPTION WHEN duplicate_column THEN NOTHING;
ROLLBACK;
In this query I am trying to add a column that already exists (playing a little bit with exceptions) and if it does then the query shall just ignore it. At the moment I am not really sure if the exception-code I am using is the right (couldn't find a site where they are described; only found this)
My Problem is if I execute this query I get the error-message:
ERROR: column "top_speed" of relation "cars" already exists
And if I execute it a second time the error-message changes to:
ERROR: current transaction is aborted, commands ignored until end of transaction block
Try an anonymous code block. As Laurenz mentioned, you were mixing PL/pgSQL and SQL commands.
Sample table
CREATE TABLE t (f1 TEXT);
Anonymous code block
DO $$
BEGIN
IF (SELECT count(column_name) FROM information_schema.columns
WHERE table_schema = 'public' AND
table_name = 't' AND
column_name = 'f2') = 0 THEN
ALTER TABLE public.t ADD COLUMN "f2" text;
END IF;
END$$;
After execution you have your new column. If the column already exists, it will do nothing.
SELECT * FROM t;
f1 | f2
----+----
0 Zeilen
In PostgreSQL 9.6+ you can use IF NOT EXISTS to check if a given column already exists in the table before creating it:
ALTER TABLE t ADD COLUMN IF NOT EXISTS f2 TEXT;
Code at db<>fiddle
Create or replace procedure sp_create_tables as
Lv_str varchar2(1000);
Begin
For I in (select distinct(deptno) from emp) loop
Lv_str:='create table deptno'||I||' select * from emp where
1=2';
Execute immediate lv_str;
End loop;
End;
From what I can understand, your question is probably "why the procedure throws this compilation error"
PLS-00306: wrong number or types of arguments in call to '||'
The reason is that the implicit cursor loop variable I refers to the set of records from the query and not the deptno itself. In order to refer to the deptno, you should use <loop_variable>.deptno. Also 2 other things you should change: The as keyword is missing and DISTINCT is a keyword and you are using it as a function, which works because of default parentheses, but is not the right way to use it.
Create or replace procedure sp_create_tables as
Lv_str varchar2(1000);
Begin
For I in (select distinct dept from emp) loop
Lv_str:='create table deptno'||I.deptno||' as select * from emp where
1=2';
Execute immediate lv_str;
End loop;
End;
In this line of code I is an implicit rowtype variable, with a data structure defined by the projection of the driving select statement:
For I in (select distinct(deptno) from emp) loop
But you are attempting to reference it in your dynamic SQL as though it were an attribute. You need to use a column name instead.
Create or replace procedure sp_create_tables as
Lv_str varchar2(1000);
Begin
For I in (select distinct (deptno) from emp) loop
Lv_str:='create table deptno'|| I.deptno ||
' as select * from emp where 1=2';
Execute immediate lv_str;
End loop;
End;
Incidentally there is a bug in your dynamic SQL statement. The correct syntax is CREATE TABLE ... AS SELECT .... Dynamic SQL is hard because the compiler can't validate the bits of code in strings. Consequently what should be compilation errors manifest themselves as runtime errors. You will find it helpful to instrument your code with some logging (or dbms_output.put_line()) to record the assembled statement before it runs. It makes debugging a lot easier.
" i have got a error saying -01031 insufficient priviliges"
So what this means is your authorisation to create a table was granted through a role. The Oracle security model does not allow us to build PL/SQL programs - or views - using privileges granted through a role. This includes PL/SQL executing DDL through dynamic SQL. You need a DBA user to grant CREATE TABLE to your user directly.
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.
I would like to know if it's possible to write a sql query that returns a set of columns based on a condition.
Like for example:
If (id=='A')
{
Select id,name
From Table A
}
Else If(Condition=B)
{
Select Column1, Column3
From Table A
}
If yes please help me write it
You can do switch-like statements with CASE expressions in plain SQL. See the following example:
SELECT some_other_field,
id,
CASE ID
WHEN A THEN columnA
WHEN B THEN columnB
ELSE 'Unknown'
END genericvalue
FROM customers;
There are some limitations of course. For example the type of the return values in the THEN clause need to match, so you may need to convert for example all to char, or to int, etc.
Syntax (IF-THEN-ELSE)
The syntax is for IF-THEN-ELSE in Oracle/PLSQL is:
IF condition THEN
{...statements to execute when condition is TRUE...}
ELSE
{...statements to execute when condition is FALSE...}
END IF;
http://www.techonthenet.com/oracle/loops/if_then.php
SQL itself isn't turing-complete and it doesn't have syntax for loops and conditions: you can perform a query with it, no matter how complex it is, but you can't decide which query to execute depending on a condition or perform a query a number of times, which is what you are trying to do here.
In order to provide such functionality each database developer typically provides an additional language that includes variable declaration, loops, conditionals, etc. For Oracle this language is PL/SQL.
What you need to do in SQL Developer to solve your issue and see how PL/SQL works is create an empty script, then write something like this:
--Enabling output to the console
SET SERVEROUTPUT ON;
DECLARE
--Variable declaration block; can initialize variables here too
test_var varchar2(10);
test_result varchar2(10);
BEGIN
--Initializing variables, the first one we will check in the IF statement, the second one is just for transparency
test_var := 'test';
test_result := '';
--IF block: check some condition, perform a select based on the value, save result into a variable
IF test_var = 'test' THEN
SELECT '1' INTO test_result FROM dual;
ELSE
SELECT '2' INTO test_result FROM dual;
END IF;
--Output the result to console
DBMS_OUTPUT.PUT_LINE(test_result);
END;
Then run it with 'Run script'/F5. You will get '1' as output as you would expect. Change test_var to something else and run it again, you will get '2'.
If you have questions of this kind it might be useful to read about what exactly SQL and PL/SQL are. PL/SQL is quite efficient and versatile and can be used for anything from automating SQL scripts to implementing complex optimisation algorithms.
Of course, PL/SQL has similar constructs for FOR and WHILE loops, CASE checks, etc.
I guess this is what you are looking at.
It is not possible to do such a selection in SQL even by using CASE and DECODE.
But the best we can do is we can create a function which returns a ref_cursor and use the function in the SQL stetement to fit your requirement.
Below is an example for it:
CREATE OR REPLACE
FUNCTION test1(
id1 VARCHAR)
RETURN sys_refcursor
AS
v_ref sys_refcursor;
BEGIN
IF(id1='A') THEN
OPEN v_ref FOR SELECT id,name FROM TABLE A;
ElsIf(id1='B') THEN
OPEN v_ref FOR SELECT Column1, Column3 FROM TABLE A;
END IF;
RETURN v_ref;
END;
select test1(A) from dual;
Above will display only the columns id and name.