Below is my problem and desired solution.
Query1:
Select colnames from table1;
Query1 Result:
col1
col2
col3
col4
Query2:
Select a1.*
from table2 a1;
-- should translate to
select a1.col1, a1.col2, a1.col3, a1.col4 from table2 a1;
My first query will give the list of column names, I need to replace the .* with those column names in my second query. How can I achieve this?
You are looking for dynamic SQL. The idea is to generate the query string from the results of a SQL query. You can then run it with execute immediate.
In your use case, that would look like:
declare
p_sql varchar2(100);
begin
select
'select '
|| listagg('a1.' || colnames, ', ') within group(order by colnames)
|| ' from table2 a1'
into p_sql
from table1;
dbms_output.put_line('sql: ' || p_sql); -- debug
execute immediate p_sql; -- execute
end;
/
For your sample data, this generates:
dbms_output:
sql: select a1.col1, a1.col2, a1.col3, a1.col4 from table2 a1
Related
Current table1:
col1
-------------
schema.table1
schema.table2
schema.table3
Desired table1:
col1 col2
------------------------------------------------------------
schema.table1 value of (select count(*) from schema.table1)
schema.table2 value of (select count(*) from schema.table1)
schema.table3 value of (select count(*) from schema.table1)
It is not working, I tried using function too, but function doesn't allow to use 'FROM'
select col1, (select count(*) from col1)
from table1
I am trying to create this query in redshift. Can anyone please help me out?
To perform this task you will need a stored procedure AND a defined cursor. The stored procedure allows for looping and the cursor provides the ability to execute a newly created statement (dynamic querying).
For example:
Create the starting materials, 3 tables and a table that references these tables.
create table foo as (select 1 as A);
create table goo as (select 2 as A);
create table hoo as (select 3 as A);
create table tabs as (select 'foo' as tab union all select 'goo' union all select 'hoo');
Next define the stored procedure the will create the dynamic SQL
CREATE OR REPLACE procedure count_tabs(curs1 INOUT refcursor)
AS
$$
DECLARE
row record;
statement varchar := '';
union_needed BOOL := false;
BEGIN
for row in select tab from tabs LOOP
IF union_needed THEN
statement := statement || ' UNION ALL ';
END IF;
statement := statement || 'select \'' || row.tab || '\' as table_name, count(*) as table_count from ' || row.tab ;
union_needed := true;
END LOOP;
RAISE NOTICE 'sql to execute: %',statement;
open curs1 for execute statement;
END;
$$ LANGUAGE plpgsql;
Lastly we need to call the procedure and execute the cursor
call count_tabs('mycursor');
fetch 1000 from mycursor;
A few notes on this:
This assumes you want the results as output on your bench. If you want to create a table with the results this is doable in the same structure
Since the FROM clause value(s) is unknown at compile time this needs to be done in 2 steps - create the query and then execute the query.
I believe you can have the procedure walk this same cursor itself but doing this is exceptionally slow
I want to select/display the columns of a table that are of a certain format. I wrote the following query:
SELECT
(SELECT
COLUMN_NAME
FROM SYS.ALL_TAB_COLS
WHERE TABLE_NAME='SOME_TABLE' AND DATA_TYPE IN ('DATE'))
FROM SOME_TABLE;
After the query runs for some time, I get the following error:
ORA-01427: single-row subquery returns more than one row
I would want a result that is something like:
DATE1 DATE2
2017-01-01 2017-01-01
2017-01-01 2018-01-02
... ...
Does someone know how to achieve this?
You could make use of a refcursor bind variable and use the PRINT command to display the output from a dynamic query. This works in SQL* Plus and in Toad and SQL developer when run as script.
VARIABLE x refcursor;
DECLARE
v_query CLOB;
BEGIN
SELECT 'SELECT '
|| LISTAGG(column_name, ',')
within GROUP ( ORDER BY column_name )
|| ' FROM '
|| table_name
INTO v_query
FROM sys.all_tab_cols
WHERE table_name = 'EMPLOYEES'
AND data_type IN ( 'DATE' )
GROUP BY table_name;
OPEN :x FOR v_query;
END;
/
PRINT x;
for 12c and above, you could use DBMS_SQL.RETURN_RESULT on a PL/SQL cursor on the same query.
DECLARE
v_query CLOB;
x SYS_REFCURSOR;
BEGIN
SELECT..
..
OPEN x FOR v_query;
DBMS_SQL.RETURN_RESULT(x);
END;
/
Note: If there are multiple tables in different schemas with the same name, you would need to add owner = <schema> as well.
Use this query to return the rows in columns and then you can use and format the columns that dynamically return with execute of EXECUTE IMMEDIATE
SELECT LISTAGG(COLUMN_NAME, ',') WITHIN GROUP(ORDER BY COLUMN_NAME) AS COLUMNA FROM (
SELECT COLUMN_NAME
FROM SYS.ALL_TAB_COLS
WHERE TABLE_NAME = 'SOME_TABLE' AND DATA_TYPE IN ('DATE')
) SOME_TABLE
RESULT:
DATE1, DATE2
I have table like this:
Table-1
Table-2
Table-3
Table-4
Table-5
each table is having many columns and one of the column name is employee_id.
Now, I want to write a query which will
1) return all the tables which is having this columns and
2) results should show the tables if the column is having values or empty values by passing employee_id.
e.g. show table name, column name from Table-1, Table-2,Table-3,... where employee_id='1234'.
If one of the table doesn't have this column, then it is not required to show.
I have verified with link, but it shows only table name and column name and not by passing some column values to it.
Also verified this, but here verifies from entire schema which I dont want to do it.
UPDATE:
Found a solution, but by using xmlsequence which is deprecated,
1)how do I make this code as xmltable?
2) If there are no values in the table, then output should have empty/null. or default as "YES" value
WITH char_cols AS
(SELECT /*+materialize */ table_name, column_name
FROM cols
WHERE data_type IN ('CHAR', 'VARCHAR2') and table_name in ('Table-1','Table-2','Table-3','Table-4','Table-5'))
SELECT DISTINCT SUBSTR (:val, 1, 11) "Employee_ID",
SUBSTR (table_name, 1, 14) "Table",
SUBSTR (column_name, 1, 14) "Column"
FROM char_cols,
TABLE (xmlsequence (dbms_xmlgen.getxmltype ('select "'
|| column_name
|| '" from "'
|| table_name
|| '" where upper("'
|| column_name
|| '") like upper(''%'
|| :val
|| '%'')' ).extract ('ROWSET/ROW/*') ) ) t ORDER BY "Table"
/
This query can be done in one step using the (non-deprecated) XMLTABLE.
Sample Schema
--Table-1 and Table-2 match the criteria.
--Table-3 has the right column but not the right value.
--Table-4 does not have the right column.
create table "Table-1" as select '1234' employee_id from dual;
create table "Table-2" as select '1234' employee_id from dual;
create table "Table-3" as select '4321' employee_id from dual;
create table "Table-4" as select 1 id from dual;
Query
--All tables with the column EMPLOYEE_ID, and the number of rows where EMPLOYEE_ID = '1234'.
select table_name, total
from
(
--Get XML results of dynamic query on relevant tables and columns.
select
dbms_xmlgen.getXMLType(
(
--Create a SELECT statement on each table, UNION ALL'ed together.
select listagg(
'select '''||table_name||''' table_name, count(*) total
from "'||table_name||'" where employee_id = ''1234'''
,' union all'||chr(10)) within group (order by table_name) v_sql
from user_tab_columns
where column_name = 'EMPLOYEE_ID'
)
) xml
from dual
) x
cross join
--Convert the XML data to relational.
xmltable('/ROWSET/ROW'
passing x.xml
columns
table_name varchar2(128) path 'TABLE_NAME',
total number path 'TOTAL'
);
Results
TABLE_NAME TOTAL
---------- -----
Table-1 1
Table-2 1
Table-3 0
Just try to use code below.
Pay your attention that may be nessecery clarify scheme name in loop.
This code works for my local db.
set serveroutput on;
DECLARE
ex_query VARCHAR(300);
num NUMBER;
emp_id number;
BEGIN
emp_id := <put your value>;
FOR rec IN
(SELECT table_name
FROM all_tab_columns
WHERE column_name LIKE upper('employee_id')
)
LOOP
num :=0;
ex_query := 'select count(*) from ' || rec.table_name || ' where employee_id = ' || emp_id;
EXECUTE IMMEDIATE ex_query into num;
if (num>0) then
DBMS_OUTPUT.PUT_LINE(rec.table_name);
end if;
END LOOP;
END;
I tried with the xml thing, but I get an error I cannot solve. Something about a zero size result. How difficult is it to solve this instead of raising exception?! Ask Oracle.
Anyway.
What you can do is use the COLS table to know what table has the employee_id column.
1) what table from table TABLE_LIKE_THIS (I assume column with table names is C) has this column?
select *
from COLS, TABLE_LIKE_THIS t
where cols.table_name = t
and cols.column_name = 'EMPLOYEE_ID'
-- think Oracle metadata/ think upper case
2) Which one has the value you are looking for: write a little chunk of Dynamic PL/SQL with EXECUTE IMMEDIATE to count the tables matching above condition
declare
v_id varchar2(10) := 'JP1829'; -- value you are looking for
v_col varchar2(20) := 'EMPLOYEE_ID'; -- column
n_c number := 0;
begin
for x in (
select table_name
from all_tab_columns cols
, TABLE_LIKE_THIS t
where cols.table_name = t.c
and cols.column_name = v_col
) loop
EXECUTE IMMEDIATE
'select count(1) from '||x.table_name
||' where Nvl('||v_col||', ''##'') = ''' ||v_id||'''' -- adding quotes around string is a little specific
INTO n_c;
if n_c > 0 then
dbms_output.put_line(n_C|| ' in ' ||x.table_name||' has '||v_col||'='||v_id);
end if;
-- idem for null values
-- ... ||' where '||v_col||' is null '
-- or
-- ... ||' where Nvl('||v_col||', ''##'') = ''##'' '
end loop;
dbms_output.put_line('done.');
end;
/
Hope this helps
I have many tables that have the same column 'customer_number'.
I can get a list of all these table by query:
SELECT table_name FROM ALL_TAB_COLUMNS
WHERE COLUMN_NAME = 'customer_number';
The question is how do I get all the records that have a specific customer number from all these tables without running the same query against each of them.
To get record from a table, you have write a query against that table. So, you can't get ALL the records from tables with specified field without a query against each one of these tables.
If there is a subset of columns that you are interested in and this subset is shared among all tables, you may use UNION/UNION ALL operation like this:
select * from (
select customer_number, phone, address from table1
union all
select customer_number, phone, address from table2
union all
select customer_number, phone, address from table3
)
where customer_number = 'my number'
Or, in simple case where you just want to know what tables have records about particular client
select * from (
select 'table1' src_tbl, customer_number from table1
union all
select 'table2', customer_number from table2
union all
select 'table3', customer_number from table3
)
where customer_number = 'my number'
Otherwise you have to query each table separatelly.
DBMS_XMLGEN enables you to run dynamic SQL statements without custom PL/SQL.
Sample Schema
create table table1(customer_number number, a number, b number);
insert into table1 values(1,1,1);
create table table2(customer_number number, a number, c number);
insert into table2 values(2,2,2);
create table table3(a number, b number, c number);
insert into table3 values(3,3,3);
Query
--Get CUSTOMER_NUMBER and A from all tables with the column CUSTOMER_NUMBER.
--
--Convert XML to columns.
select
table_name,
to_number(extractvalue(xml, '/ROWSET/ROW/CUSTOMER_NUMBER')) customer_number,
to_number(extractvalue(xml, '/ROWSET/ROW/A')) a
from
(
--Get results as XML.
select table_name,
xmltype(dbms_xmlgen.getxml(
'select customer_number, a from '||table_name
)) xml
from user_tab_columns
where column_name = 'CUSTOMER_NUMBER'
);
TABLE_NAME CUSTOMER_NUMBER A
---------- --------------- -
TABLE1 1 1
TABLE2 2 2
Warnings
These overly generic solutions often have issues. They won't perform as well as a plain old SQL statements and they are more likely to run into bugs. In general, these types of solutions should be avoided for production code. But they are still very useful for ad hoc queries.
Also, this solution assumes that you want the same columns from each row. If each row is different then things get much more complicated and you may need to look into technologies like ANYDATASET.
I assume you want to automate this. Two approaches.
SQL to generate SQL scripts
.
spool run_rep.sql
set head off pages 0 lines 200 trimspool on feedback off
SELECT 'prompt ' || table_name || chr(10) ||
'select ''' || table_name ||
''' tname, CUSTOMER_NUMBER from ' || table_name || ';' cmd
FROM all_tab_columns
WHERE column_name = 'CUSTOMER_NUMBER';
spool off
# run_rep.sql
PLSQL
Similar idea to use dynamic sql:
DECLARE
TYPE rcType IS REF CURSOR;
rc rcType;
CURSOR c1 IS SELECT table_name FROM all_table_columns WHERE column_name = 'CUST_NUM';
cmd VARCHAR2(4000);
cNum NUMBER;
BEGIN
FOR r1 IN c1 LOOP
cmd := 'SELECT cust_num FROM ' || r1.table_name ;
OPEN rc FOR cmd;
LOOP
FETCH rc INTO cNum;
EXIT WHEN rc%NOTFOUND;
-- Prob best to INSERT this into a temp table and then
-- select * that to avoind DBMS_OUTPUT buffer full issues
DBMS_OUTPUT.PUT_LINE ( 'T:' || r1.table_name || ' C: ' || rc.cust_num );
END LOOP;
CLOSE rc;
END LOOP;
END;
I'm writing SQL (for Oracle) like:
INSERT INTO Schema1.tableA SELECT * FROM Schema2.tableA;
where Schema1.tableA and Schema2.tableA have the same columns. However, it seems like this is unsafe, since the order of the columns coming back in the SELECT is undefined. What I should be doing is:
INSERT INTO Schema1.tableA (col1, col2, ... colN)
SELECT (col1, col2, ... colN) FROM Schema2.tableA;
I'm doing this for lots of tables using some scripts, so what I'd like to do is write something like:
INSERT INTO Schema1.tableA (foo(Schema1.tableA))
SELECT (foo(Schema1.tableA)) FROM Schema2.tableA;
Where foo is some nifty magic that extracts the column names from table one and packages them in the appropriate syntax. Thoughts?
This PL/SQL should do it:
declare
l_cols long;
l_sql long;
begin
for r in (select column_name from all_tab_columns
where table_name = 'TABLEA'
and owner = 'SCHEMA1'
)
loop
l_cols := l_cols || ',' || r.column_name;
end loop;
-- Remove leading comma
l_cols := substr(l_cols, 2);
l_sql := 'insert into schema1.tableA (' || l_cols || ') select '
|| l_cols || ' from schema2.tableA';
execute immediate l_sql;
end;
/
You may need to construct the insert statements dynamically using USER_TAB_COLUMNS and execute them using EXECUTE IMMEDIATE.