It is possible to build a statement using variables for the table name without creating a VARCHAR and using EXECUTE IMMEDIATE?
ex:
#table_name := test_table
UPDATE #table_name
SET col1 = val1
WHERE condition...;
this is my actual workaround:
DECLARE
sql_stmt VARCHAR2(1000);
table_name VARCHAR2(30) := 'test_table';
BEGIN
sql_stmt := 'UPDATE ' || table_name || ' SET col1 = val1...';
EXECUTE IMMEDIATE sql_stmt;
END;
/
"[Is it] possible to build a statement using variables for the table
name without creating a VARCHAR and using EXECUTE IMMEDIATE?"
No.
SQL is a strongly typed language. The compiler requires the actual table name in order to validate the various components of the SQL statement ( projection, filters, etc).
Dynamic SQL (EXECUTE IMMEDIATE and DBMS_SQL) is necessary to short-circuit the compile time validation. Essentially it's a mechanism relieving the compiler of the burden of verifying the SQL and taking it on ourselves (because humans are so much better at such jobs than machines. Not).
Alternatively, it's a mechanism for generating runtime errors instead of compilation errors.
Either way, it's pretty odd to know the name of the COLUMN in the filter but not the name of the TABLE being updated.
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)
Can I execute a select query stored as a Varchar in another table's column ??.
Suppose there is a table TB_SQL_QUERIES, with column name as SQL_QUERY_TEXT and ID.
Is there a way to execute a query from this table where ID=(to be input by the user)
Yes, you would do something like:
DECLARE
l_sql VARCHAR2(4000);
BEGIN
SELECT sql_query_text INTO l_sql
FROM tb_sql_queries
WHERE id = 1;
EXECUTE IMMEDIATE l_sql;
END;
See EXECUTE IMMEDIATE.
Inprovising on the other answer about EXECUTE IMMEDIATE :
Firstly, in 12c, you can have 32767 for SQL rather than the limitation of 4000 in prior versions. Thus, you can eliminate the effort to have multiple variables to keep concatenating the dynamic string whenever it exceeds 4000 characters.
Secondly, since you mentioned that the input would be by user, you need to have Bind variable to get the value at run time.
If i type my source tables name, data are copy into our target table:
'Create or Replace procedure p
(source_tab varchar2,target_tab varchar2)
As
query varchar2(200);
Type I_tab is table of varchar2(100000) index by binary_integer;
Rec_i I_tab;
Begin
query=’select * from’||source_tab;
Execute immediate query bulk collect into rec_i;
Forall i in rec_i.first..rec_i.last
Execute immediate’insert into’||target_tab||’values’||rec_i(i);
Commit;
End;
/
In the absence of anything useful like the actual compilation or runtime errors are we can do is guess.
As it happens your code has several obvious bloomers.
You appear to be using MS Word type smart quotes ’ whereas Oracle expects regular ASCII dumb quotes '. So that would be a compilation error.
The maximum size of a VARCHAR2 is 32767 so your nested table statement will hurl a compilation error.
You need to put spaces around the key words in the dynamic SQL. Otherwise you'll get a runtime error. So ’insert into’||target_tab||’values’ needs to 'insert into '||target_tab||' values ' . Make sure you check all the strings.
In PL/SQL the assignment operator is :=; = is the test for equality.
Less obvious, but we can't use EXECUTE IMMEDIATE in a FORALL. It's not a programmatic loop, and it needs to be a DML (SQL) statement: EXECUTE IMEMDIATE is PL/SQL. However you can do the same thing with
execute immediate
'insert into '|| target_tab ||
' select * from '|| source_tab
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
This question is similar to a couple others I have found on StackOverflow, but the differences are signficant enough to me to warrant a new question, so here it is:
I want to obtain a result set from dynamic SQL in Oracle and then display it as a result set in a SqlDeveloper-like tool, just as if I had executed the dynamic SQL statement directly. This is straightforward in SQL Server, so to be concrete, here is an example from SQL Server that returns a result set in SQL Server Management Studio or Query Explorer:
EXEC sp_executesql N'select * from countries'
Or more properly:
DECLARE #stmt nvarchar(100)
SET #stmt = N'select * from countries'
EXEC sp_executesql #stmt
The question "How to return a resultset / cursor from a Oracle PL/SQL anonymous block that executes Dynamic SQL?" addresses the first half of the problem--executing dynamic SQL into a cursor. The question "How to make Oracle procedure return result sets" provides a similar answer. Web search has revealed many variations of the same theme, all addressing just the first half of my question. I found this post explaining how to do it in SqlDeveloper, but that uses a bit of functionality of SqlDeveloper. I am actually using a custom query tool so I need the solution to be self-contained in the SQL code. This custom query tool similarly does not have the capability to show output of print (dbms_output.put_line) statements; it only displays result sets. Here is yet one more possible avenue using 'execute immediate...bulk collect', but this example again renders the results with a loop of dbms_output.put_line statements. This link attempts to address the topic but the question never quite got answered there either.
Assuming this is possible, I will add one more condition: I would like to do this without having to define a function or procedure (due to limited DB permissions). That is, I would like to execute a self-contained PL/SQL block containing dynamic SQL and return a result set in SqlDeveloper or a similar tool.
So to summarize:
I want to execute an arbitrary SQL statement (hence dynamic SQL).
The platform is Oracle.
The solution must be a PL/SQL block with no procedures or functions.
The output must be generated as a canonical result set; no print statements.
The output must render as a result set in SqlDeveloper without using any SqlDeveloper special functionality.
Any suggestions?
The closest thing I could think of is to create a dynamic view for which permission is required. This will certainly involve using a PL/SQL block and a SQL query and no procedure/function. But, any dynamic query can be converted and viewed from the Result Grid as it's going to be run as a select query.
DEFINE view_name = 'my_results_view';
SET FEEDBACK OFF
SET ECHO OFF
DECLARE
l_view_name VARCHAR2(40) := '&view_name';
l_query VARCHAR2(4000) := 'SELECT 1+level as id,
''TEXT''||level as text FROM DUAL ';
l_where_clause VARCHAR2(4000):=
' WHERE TRUNC(1.0) = 1 CONNECT BY LEVEL < 10';
BEGIN
EXECUTE IMMEDIATE 'CREATE OR REPLACE VIEW '
|| l_view_name
|| ' AS '
|| l_query
|| l_where_clause;
END;
/
select * from &view_name;
You seem to be asking for a chunk of PL/SQL code that will take an arbitrary query returning result set of undetermined structure and 'forward/restructure' that result set in some way such that is can easily be rendered by some "custom GUI tool".
If so, look into the DBMS_SQL for dynamic SQL. It has a DESCRIBE_COLUMNS procedure which returns the columns from a dynamic SELECT statement. The steps you would need are,
Parse the statement
Describe the result set (column names and data types)
Fetch each row, and for each column, call the datatype dependent function to return that value into a local variable
Place those local variables into a defined structure to return to the calling environment (eg consistent column names [such as col_1, col_2] probably all of VARCHAR2)
As an alternative, you could try building the query into an XMLFOREST statement, and parse the results out of the XML.
Added :
Unlike SQL Server, an Oracle PL/SQL call will not 'naturally' return a single result set. It can open up one or more ref cursors and pass them back to the client. It then becomes the client's responsibility to fetch records and columns from those ref cursors. If your client doesn't/can't deal with that, then you cannot use a PL/SQL call.
A stored function can return a pre-defined collection type, which can allow you to do something like "select * from table(func_name('select * from countries'))". However the function cannot do DML (update/delete/insert/merge) because it blows away any concept of consistency for that query. Plus the structure being returned is fixed so that
select * from table(func_name('select * from countries'))
must return the same set of columns (column names and data types) as
select * from table(func_name('select * from persons'))
It is possible, using DBMS_SQL or XMLFOREST, for such a function to take a dynamic query and restructure it into a pre-defined set of columns (col_1, col_2, etc) so that it can be returned in a consistent manner. But I can't see what the point of it would be.
Try try these.
DECLARE
TYPE EmpCurTyp IS REF CURSOR;
v_emp_cursor EmpCurTyp;
emp_record employees%ROWTYPE;
v_stmt_str VARCHAR2(200);
v_e_job employees.job%TYPE;
BEGIN
-- Dynamic SQL statement with placeholder:
v_stmt_str := 'SELECT * FROM employees WHERE job_id = :j';
-- Open cursor & specify bind argument in USING clause:
OPEN v_emp_cursor FOR v_stmt_str USING 'MANAGER';
-- Fetch rows from result set one at a time:
LOOP
FETCH v_emp_cursor INTO emp_record;
EXIT WHEN v_emp_cursor%NOTFOUND;
END LOOP;
-- Close cursor:
CLOSE v_emp_cursor;
END;
declare
v_rc sys_refcursor;
begin
v_rc := get_dept_emps(10); -- This returns an open cursor
dbms_output.put_line('Rows: '||v_rc%ROWCOUNT);
close v_rc;
end;
Find more examples here. http://forums.oracle.com/forums/thread.jspa?threadID=886365&tstart=0
In TOAD when executing the script below you will be prompted for the type of v_result. From the pick list of types select cursor, the results are then displayed in Toad's data grid (the excel spreadsheet like result). That said, when working with cursors as results you should always write two programs (the client and the server). In this case 'TOAD' will be the client.
DECLARE
v_result sys_refcursor;
v_dynamic_sql VARCHAR2 (4000);
BEGIN
v_dynamic_sql := 'SELECT * FROM user_objects where ' || ' 1 = 1';
OPEN :v_result FOR (v_dynamic_sql);
END;
There may be a similar mechanism in Oracle's SQL Developer to prompt for the binding as well.