I would like to create the following index
CREATE INDEX timevariable_idx_varvalue_projectid
ON timevariable (varvalue,projectid);
only if does not exist, but I'm having a hard time doing it
would anyone know how to do so?!
Unfortunately Oracle does not support the IF NOT EXISTS clause to CREATE statements (I don't know about APEX though, which you also tagged your question with).
So you need execute immediate in a code block. This Ask TOM article gives an elegant solution that works by trapping exceptions.
Adapted to your use case, this would be:
set serveroutput on
declare
already_exists exception;
columns_indexed exception;
pragma exception_init(already_exists, -955);
pragma exception_init(columns_indexed, -1408);
begin
execute immediate 'create index timevariable_idx_varvalue_projectid ON timevariable (varvalue,projectid)';
dbms_output.put_line('created');
exception
when already_exists or columns_indexed then
dbms_output.put_line('skipped');
end;
Oracle has no "IF NOT EXISTS" syntax in its DDL commands. If you execute the CREATE command, you either need to accept the error in your script as ok to ignore, or handle the error in some way. If you want to avoid the execute commend unless necessary, you'd need to check the data dictionary for the index first, then execute if required:
declare
l_count number;
begin
select count(*) into l_count from dba_indexes where index_name='TIMEVARIABLE_IDX_VARVALUE_PROJECTID';
if l_count = 0 then
execute immediate 'CREATE INDEX timevariable_idx_varvalue_projectid ON timevariable (varvalue,projectid)';
end if;
end;
Related
I am using execute immediate to create table and use this table into my code to insert some values when i run this code .it gives me error that table and view does not exist.why?. this code has ability to create table because when i use drop and create table command with existing table by using execute immediate then my code works fine and when i just remove drop table syntax, my code does not work, Please help me to clear my concept about dynamic SQL-----------
SET serveroutput ON
DECLARE
ddl_table VARCHAR2(200);
r_emp SYS.ODCINUMBERLIST := SYS.ODCINUMBERLIST();
v_array SYS.ODCIVARCHAR2LIST := SYS.ODCIVARCHAR2LIST('ACCT_ID',
'PARENT_ACCT_ID',
'CUST_ID',
'ACCT_NAME',
'BILLING_CYCLE_TYPE',
'PAID_FLAG',
'BILL_DELIVER_METHOD');
BEGIN
ddl_table := 'CREATE TABLE test123(
v_column VARCHAR2(50),
v_count NUMBER
)';
EXECUTE IMMEDIATE ddl_table;
DBMS_OUTPUT.ENABLE;
FOR i IN 1 .. v_array.COUNT LOOP
r_emp.EXTEND;
EXECUTE IMMEDIATE 'SELECT COUNT(*)
FROM account_profile
WHERE NOT REGEXP_LIKE(' ||v_array(i) || ',''[A-Za-z0-9.]'')'
INTO r_emp(i);
IF r_emp(i) <> 0 THEN
DBMS_OUTPUT.PUT_LINE(v_array(i) || ': ' || r_emp(i));
INSERT INTO test123 VALUES (v_array(i), r_emp(i));
END IF;
END LOOP;
END;
/
Error report -
ORA-06550: line 24, column 17:
PL/SQL: ORA-00942: table or view does not exist
Your problem is that the annonymous block is pre-validated (pre-compiled) before it is valid. Oracle will check all objects in use before executing it. Since you are creating test123 dynamically it doesn't exist so your insert statement fails.
You can instead, use an EXECUTE IMMEDIATE command to also insert the data on your test123 table.
The way you use the EXECUTE IMMEDIATE for an insert command is either concatenating the parameters or preparing them, I prefer the later. Like this
execute immediate 'insert into test123 values (:param1,:param2)' using v_array(i), r_emp(i);
Here is the official documentation for the EXECUTE IMMEDIATE command.
Though it shows how it works and explain the usage of it, it doesn't particularly answer you direct question on the comments.
So
can you explain :param1,:param2
Those are called "binding" parameters that will be replaced by the variables used after the using statement. It doesn't matter their name only the order in which they appear on the string. The number of parameters within the dynamic string needs to match the number of parameters after the using statement.
why we use it with : colon and what are these
The colon : there is just to make it easier for the parser to know what to replace and where when using the variables you provided after the using statement
Translating that execute immediate it would be something like this:
... values (:param1,:param2)' using v_array(i), r_emp(i)
Hey "execute immediate" whenever you see :param1 please replace it with the content of the variable I'm providing as v_array(i) and whenever you see :param2 please replace it with the content of the variable I'm providing as r_emp(i)
I am writing a deployment script that includes a MERGE into a view that may or may not exist in one of many target schemas (schemii? schemata?).
I am attempting this SQL:
DECLARE
BEGIN
/* MERGE statement that will work if the view is available */
EXCEPTION
WHEN OTHERS THAN
DBMS_OUTPUT.put_line('warning: merge target is not available');
END;
When I run this block I get the standard "PL/SQL: ORA-00942: table or view does not exists" error.
How can I trap this error and generate a warning line instead?
Combining the valid answers with the suggested improvements, it all came together as:
SET SERVEROUTPUT ON;
PROMPT ...trying UPSERT;
DECLARE
eTableNotExists exception;
pragma exception_init(eTableNotExists, -00942);
BEGIN
EXECUTE IMMEDIATE '<MERGE statement that will work if the view is available--no trailing ";"!>';
DBMS_OUTPUT.put_line('insert worked');
EXCEPTION
WHEN eTableNotExists THEN
DBMS_OUTPUT.put_line('FYI: doesn''t exist on this schema');
END;
/
COMMIT;
SET SERVEROUTPUT OFF;
(SERVEROUTPUT sets were necessary to see results of DBMS_OUTPUT.put_line())
You need to use dynamic SQL:
BEGIN
EXECUTE IMMEDIATE 'MERGE ...';
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.put_line('warning: merge target is not available');
END;
You can use dynamic SQL to postpone such an error to run time and catch it
EXECUTE IMMEDIATE '<MERGE>'
instead of "static" MERGE
I have implemented a certain feature in my application where the user can compose queries dynamically from the user interface by pushing around buttons and inserting some values here and there.
The user will not see the generated SQL statement at all.
I was wondering if there is a way to perhaps check the syntax and grammar (e.g. he opened a parantheses '(' and forgot to close it ) of the dynamically generated SQL to ensure that no run-time compilation errors would happen before actually executing the statement using EXECUTE IMMEDIATE.
You could use the dbms_sql.parse procedure to parse the SQL statement assuming the statement is DML not DDL. It would be rather unusual to parse a dynamic SQL statement using the dbms_sql package and then use EXECUTE IMMEDIATE to execute it rather than using dbms_sql.execute but nothing prevents you from mixing dbms_sql and execute immediate.
The code to just parse the SQL statement would be something like
DECLARE
l_cursor integer;
l_sql_stmt varchar2(1000) := <<some SQL statement>>;
BEGIN
l_cursor := dbms_sql.open_cursor;
dbms_sql.parse( l_cursor, l_sql_stmt, dbms_sql.native );
dbms_sql.close_cursor( l_cursor );
END;
You can also use explain plan, this is basically doing the first step of the execution.
SQL> explain plan for select * from dual;
Explained.
SQL is valid, you can also use the explain tables to get the tables, views etc, maybe even estimated run time ...
SQL> explain plan for select * from duall;
explain plan for select * from duall
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL is invalid, this is why ...
you can also use it in a dynamic statement
SQL> begin execute immediate 'explain plan for ' || ' select * from dual'; end;
2 /
PL/SQL procedure successfully completed.
As always use error-handling, e.g. write a little error log creater package or procedure what u call when it's needed.
DECLARE
my_stmt VARCHAR2(4000):='this will contain my statements';
BEGIN
'begin' || my_stmt || 'end';
EXCEPTION
WHEN OTHERS THEN
prc_my_error_log_creator();
END;
in the log_creator use for example the DBMS_UTILITY.FORMAT_ERROR_BACKTRACE() func to get the stack's contain.
Regards
I am trying the code below to create a table in PL/SQL:
DECLARE
V_NAME VARCHAR2(20);
BEGIN
EXECUTE IMMEDIATE 'CREATE TABLE TEMP(NAME VARCHAR(20))';
EXECUTE IMMEDIATE 'INSERT INTO TEMP VALUES(''XYZ'')';
SELECT NAME INTO V_NAME FROM TEMP;
END;
/
The SELECT statement fails with this error:
PL/SQL: ORA-00942: table or view does not exist
Is it possible to CREATE, INSERT and SELECT all in a single PL/SQL Block one after other?
I assume you're doing something like the following:
declare
v_temp varchar2(20);
begin
execute immediate 'create table temp(name varchar(20))';
execute immediate 'insert into temp values(''XYZ'')';
select name into v_name from temp;
end;
At compile time the table, TEMP, does not exist. It hasn't been created yet. As it doesn't exist you can't select from it; you therefore also have to do the SELECT dynamically. There isn't actually any need to do a SELECT in this particular situation though you can use the returning into syntax.
declare
v_temp varchar2(20)
begin
execute immediate 'create table temp(name varchar2(20))';
execute immediate 'insert into temp
values(''XYZ'')
returning name into :1'
returning into v_temp;
end;
However, needing to dynamically create tables is normally an indication of a badly designed schema. It shouldn't really be necessary.
I can recommend René Nyffenegger's post "Why is dynamic SQL bad?" for reasons why you should avoid dynamic SQL, if at all possible, from a performance standpoint. Please also be aware that you are much more open to SQL injection and should use bind variables and DBMS_ASSERT to help guard against it.
If you run the program multiple time you will get an error even after modifying the program to run the select statement as dynamic SQL or using a returning into clause.
Because when you run the program first time it will create the table without any issue but when you run it next time as the table already created first time and you don't have a drop statement it will cause an error: "Table already exists in the Database".
So my suggestion is before creating a table in a pl/sql program always check if there is any table with the same name already exists in the database or not. You can do this check using a Data dictionary views /system tables which store the metadata depending on your database type.
For Example in Oracle you can use following views to decide if a tables needs to be created or not:
DBA_TABLES ,
ALL_TABLES,
USER_TABLES
In PL/SQL,I would like to pass a source as well as the target schema as a parameter to a stored procedure. For source we can use:
PROCEDURE select_from_schema( the_schema VARCHAR2)
IS
TYPE my_cursor_type IS REF CURSOR;
my_cursor my_cursor_type;
BEGIN
OPEN my_cursor FOR 'SELECT my_field FROM '||the_schema||'.my_table';
-- Do your FETCHes just as with a normal cursor
CLOSE my_cursor;
END;
For the target insert or update statement, how can we use that schema inside that insert or update statement....Does anyone know how could I do that???
P.S. Excuse me; I am a beginner and must get some functions written quickly.
You can do the same thing for an INSERT or UPDATE that you did for a SELECT - use dynamic SQL like this:
EXECUTE IMMEDIATE 'INSERT INTO '||target_schema||'.my_table (col1,col2...) VALUES(:val1, :val2...)' USING my_row.col1, my_row.col2...;