Creating dynamic SQL select from table columns - sql

Question

I need a to create an sql script which from a table table will build a dynamic sql request in the following way:
select ID || ',' || NAME || ',' || CODE
from TABLE_TEST;
The table name is received as an input parameter.
My SQL script is as follows;
spool exportTable.log
SET HEAD OFF
SET TRIMOUT ON
SET TRIMSPOOL ON
SET LINESIZE 32000
SET PAGESIZE 0
SET TERMOUT OFF
SET ECHO OFF
SET COLSEP ,
procedure CreerReq(sTable in Varchar) is
dbms_output.put_line('dans CreerReq');
sqlreq VARCHAR2(2000);
sChaine VARCHAR2(4000):='select';
TYPE t_tab IS TABLE OF VARCHAR2(4000);
l_tab t_tab;
l_tab_Id t_tab;
l_ref_cursor SYS_REFCURSOR;
dbms_output.put_line(sChaine);
begin
sqlreq := 'select column_name from all_tab_cols WHERE table_name' || sTable;
dbms_output.put_line(sqlreq);
OPEN l_ref_cursor FOR sqlreq;
LOOP
FETCH l_ref_cursor BULK COLLECT INTO l_tab_Id,l_tab limit 1000;
EXIT WHEN l_tab.COUNT=0;
FOR i IN l_tab.first .. l_tab.last LOOP
sChaine:=l_tab(i) ' || ','';
END LOOP;
CLOSE l_ref_cursor;
dbms_output.put_line(sChaine);
End CreerReq;
BEGIN
dbms_output.put_line('&1');
CreerReq(&1);
END;
/
spool off;
However this is returning me the following error:
ORA-00900: invalid SQL statement
Any help please?

Answer 1

CREATE or replace FUNCTION build_select (
p_owner IN VARCHAR2
, p_table_name IN VARCHAR2
)
RETURN VARCHAR2
AS
l_ret VARCHAR2 (32767);
BEGIN
FOR eachcol IN ( SELECT column_name
, LEAD (column_name)
OVER (
PARTITION BY table_name ORDER BY column_id
)
next_column
FROM all_tab_cols
WHERE owner = p_owner
AND table_name = p_table_name
ORDER BY column_id)
LOOP
l_ret := l_ret || eachcol.column_name || CASE WHEN eachcol.next_column IS NULL THEN NULL ELSE ',' END;
END LOOP;
IF l_ret IS NULL
THEN
raise_application_error (-20001, 'table ' || p_owner || '.' || p_table_name || ' not found');
END IF;
l_ret := 'select ' || l_ret || ' from ' || p_owner || '.' || p_table_name;
RETURN l_ret;
END build_select;
So let's test it out:
begin dbms_output.put_line(build_select('SYS', 'ALL_TAB_COLS')); end;
Results in:
select OWNER,TABLE_NAME,COLUMN_NAME,DATA_TYPE,DATA_TYPE_MOD,DATA_TYPE_OWNER,DATA_LENGTH,DATA_PRECISION,DATA_SCALE,NULLABLE,COLUMN_ID,DEFAULT_LENGTH,DATA_DEFAULT,NUM_DISTINCT,LOW_VALUE,HIGH_VALUE,DENSITY,NUM_NULLS,NUM_BUCKETS,LAST_ANALYZED,SAMPLE_SIZE,CHARACTER_SET_NAME,CHAR_COL_DECL_LENGTH,GLOBAL_STATS,USER_STATS,AVG_COL_LEN,CHAR_LENGTH,CHAR_USED,V80_FMT_IMAGE,DATA_UPGRADED,HIDDEN_COLUMN,VIRTUAL_COLUMN,SEGMENT_COLUMN_ID,INTERNAL_COLUMN_ID,HISTOGRAM,QUALIFIED_COL_NAME from SYS.ALL_TAB_COLS
Here is a simpler build_select function:
CREATE OR REPLACE FUNCTION build_select (
p_owner IN VARCHAR2
, p_table_name IN VARCHAR2
)
RETURN VARCHAR2
AS
l_ret VARCHAR2 (32767);
BEGIN
SELECT
LISTAGG (column_name, ',') WITHIN GROUP (ORDER BY column_id)
INTO l_ret
FROM all_tab_cols
WHERE table_name = p_table_name
AND owner = p_owner;
IF l_ret IS NULL
THEN
raise_application_error (-20001, 'table ' || p_owner || '.' || p_table_name || ' not found');
END IF;
l_ret := 'select ' || l_ret || ' from ' || p_owner || '.' || p_table_name;
RETURN l_ret;
END build_select;

Answer 2

I haven't worked with oracle in a while. But on sql server this is how it can be done. Look through this code and it might point you to the right direction:
/* This stored procedure builds dynamic SQL and executes
using sp_executesql */
Create Procedure sp_EmployeeSelect
/* Input Parameters */
#EmployeeName NVarchar(100),
#Department NVarchar(50),
#Designation NVarchar(50),
#StartDate DateTime,
#EndDate DateTime,
#Salary Decimal(10,2)
AS
Set NoCount ON
/* Variable Declaration */
Declare #SQLQuery AS NVarchar(4000)
Declare #ParamDefinition AS NVarchar(2000)
/* Build the Transact-SQL String with the input parameters */
Set #SQLQuery = 'Select * From tblEmployees where (1=1) '
/* check for the condition and build the WHERE clause accordingly */
If #EmployeeName Is Not Null
Set #SQLQuery = #SQLQuery + ' And (EmployeeName = #EmployeeName)'
If #Department Is Not Null
Set #SQLQuery = #SQLQuery + ' And (Department = #Department)'
If #Designation Is Not Null
Set #SQLQuery = #SQLQuery + ' And (Designation = #Designation)'
If #Salary Is Not Null
Set #SQLQuery = #SQLQuery + ' And (Salary >= #Salary)'
If (#StartDate Is Not Null) AND (#EndDate Is Not Null)
Set #SQLQuery = #SQLQuery + ' And (JoiningDate
BETWEEN #StartDate AND #EndDate)'
/* Specify Parameter Format for all input parameters included
in the stmt */
Set #ParamDefinition = ' #EmployeeName NVarchar(100),
#Department NVarchar(50),
#Designation NVarchar(50),
#StartDate DateTime,
#EndDate DateTime,
#Salary Decimal(10,2)'
/* Execute the Transact-SQL String with all parameter value's
Using sp_executesql Command */
Execute sp_Executesql #SQLQuery,
#ParamDefinition,
#EmployeeName,
#Department,
#Designation,
#StartDate,
#EndDate,
#Salary
If ##ERROR <> 0 GoTo ErrorHandler
Set NoCount OFF
Return(0)
ErrorHandler:
Return(##ERROR)
GO