I have a case where I have to choose 100 columns out of 240 columns in select statement for that I have used below query to get those 100 column but couldn't use them in select statement
Query:
select listagg(column_name,',') within group (order by column_name) as col_name
from all_tab_cols
where lower(column_name) like 'test%'
Result:
col_name
-----------------------------
test1,test2,test3,....test100
Expected output:
use those resulted values in select statement
select test1,test2,test3.... test100
from table;
Thanks in advance
Dynamic query is what you wanted here. You can use below two query inside Stored Procedure or Functions.
select listagg(column_name,',') WITHIN GROUP (ORDER BY column_name) as col_name INTO VAR_COL_DETAILS
from all_tab_cols
where lower(column_name) like 'test%'
execute IMMIDEATE 'SELECT '||VAR_COL_DETAILS|| 'FROM TABLE_NAME';
Related
How to 'group by' a query using an alias, for example:
select count(*), (select * from....) as alias_column
from table
group by alias_column
I get 'alias_column' : INVALID_IDENTIFIER error message. Why? How to group this query?
select
count(count_col),
alias_column
from
(
select
count_col,
(select value from....) as alias_column
from
table
) as inline
group by
alias_column
Grouping normally works if you repeat the respective expression in the GROUP BY clause. Just mentioning an alias is not possible, because the SELECT step is the last step to happen the execution of a query, grouping happens earlier, when alias names are not yet defined.
To GROUP BY the result of a sub-query, you will have to take a little detour and use an nested query, as indicated above.
Nest the query with the alias column:
select count(*), alias_column
from
( select empno, (select deptno from emp where emp.empno = e.empno) as alias_column
from emp e
)
group by alias_column;
select count(*), (select * from....) as alias_column
from table
group by (select * from....)
In Oracle you cannot use an alias in a group by clause.
To use an alias in Oracle you need to ensure that the alias has been defined by your query at the point at which the alias is being used.
The most straightforward way to do this is to simply treat the original query as a subquery -- in this case,
select count(*), (select * from....) as alias_column
from table
group by (select * from....)
becomes
select count, alias_column
from
(select count(*) as count, (select * from....) as alias_column
from table)
group by alias_column
I can't speak to the performance implications, but it's very quick to write if you're trying to re-use an alias in your query - throw everything in parentheses and jump up a level...
If you don't have to use an alias you could do it this way:
select
EXTRACT(year from CURRENT_DATE), count(*) from something
group by EXTRACT(year from CURRENT_DATE)
order by EXTRACT(year from CURRENT_DATE)
Instead of using alias and subquery.
I have a function, which will get greatest of three dates from the table.
create or replace FUNCTION fn_max_date_val(
pi_user_id IN number)
RETURN DATE
IS
l_modified_dt DATE;
l_mod1_dt DATE;
l_mod2_dt DATE;
ret_user_id DATE;
BEGIN
SELECT MAX(last_modified_dt)
INTO l_modified_dt
FROM table1
WHERE id = pi_user_id;
-- this table contains a million records
SELECT nvl(MAX(last_modified_ts),sysdate-90)
INTO l_mod1_dt
FROM table2
WHERE table2_id=pi_user_id;
-- this table contains clob data, 800 000 records, the table 3 does not have user_id and has to fetched from table 2, as shown below
SELECT nvl(MAX(last_modified_dt),sysdate-90)
INTO l_mod2_dt
FROM table3
WHERE table2_id IN
(SELECT id FROM table2 WHERE table2_id=pi_user_id
);
execute immediate 'select greatest('''||l_modified_dt||''','''||l_mod1_dt||''','''||l_mod2_dt||''') from dual' into ret_user_id;
RETURN ret_user_id;
EXCEPTION
WHEN OTHERS THEN
return SYSDATE;
END;
this function works perfectly fine and executes within a second.
-- random user_id , just to test the functionality
SELECT fn_max_date_val(100) as max_date FROM DUAL
MAX_DATE
--------
27-02-14
For reference purpose i have used the table name as table1,table2 and table3 but my business case is similar to what i stated below.
I need to get the details of the table1 along with the highest modified date among the three tables.
I did something like this.
SELECT a.id,a.name,a.value,fn_max_date_val(id) as max_date
FROM table1 a where status_id ='Active';
The above query execute perfectly fine and got result in millisecods. But the problem came when i tried to use order by.
SELECT a.id,a.name,a.value,a.status_id,last_modified_dt,fn_max_date_val(id) as max_date
FROM table1 where status_id ='Active' a
order by status_id desc,last_modified_dt desc ;
-- It took almost 300 seconds to complete
I tried using index also all the values of the status_id and last_modified, but no luck. Can this be done in a right way?
How about if your query is like this?
select a.*, fn_max_date_val(id) as max_date
from
(SELECT a.id,a.name,a.value,a.status_id,last_modified_dt
FROM table1 where status_id ='Active' a
order by status_id desc,last_modified_dt desc) a;
What if you don't use the function and do something like this:
SELECT a.id,a.name,a.value,a.status_id,last_modified_dt x.max_date
FROM table1 a
(
select max(max_date) as max_date
from (
SELECT MAX(last_modified_dt) as max_date
FROM table1 t1
WHERE t1.id = a.id
union
SELECT nvl(MAX(last_modified_ts),sysdate-90) as max_date
FROM table2 t2
WHERE t2.table2_id=a.id
...
) y
) x
where a.status_id ='Active'
order by status_id desc,last_modified_dt desc;
Syntax might contain errors, but something like that + the third table in the derived table too.
I just recently found out that subqueries are not allowed in INSERT statements that are inside stored procedures. This is my script:
begin
execute immediate 'truncate table itcustadm.GL_DTPJ_TEST2';
insert into GL_DTPJ_TEST2
(rule_no,
posted_by_user_id,
transaction_id,
transaction_sr_no,
dr_amount,
cr_amount,
tran_crncy_code,
bkdt_tran_flg,
bank_desc
)
select
tq.rule_no,
tq.posted_by_user_id,
tq.transaction_id,
tq.transaction_sr_no,
tq.dr_amount,
tq.cr_amount,
tq.tran_crncy_code,
tq.bkdt_tran_flg,
(select ent.bank_desc from crmuser.end ent where ent.bank_id = gam.bank_id);
But since the (select ent.bank_desc from crmuser.end ent where ent.bank_id = gam.bank_id) at the bottom of the SELECT statement is not allowed by Oracle, what's the best way to accomplish this?
I actually have this code right before the INSERT statement, but I don't know how to exactly use it:
get_bank_desc := '(select ent.bank_desc from crmuser.end ent ' ||
'where ent.bank_id = gam.bank_id)';
I am not sure what you are exactly trying for, but below code may be useful for you, you can achieve inserting a SubQuery output into a table using below query sample, but make sure output of the SubQuery is a single row o/p, so that you can escape from "ORA-01427: single-row SubQuery returns more than one row" ERROR.
insert into test_ins1
values(1,(SELECT COL2 FROM TEST_INS WHERE COL1=1 ));
Even then you can use rownum in where condition and take the single value.
Please let me know in case of any doubts
declare
bank_desc_temp bank_desk_type; /* the type defined in crmuser.ent for bank_desc*/
begin
select ent.bank_desc into bank_desc_temp from crmuser.end ent where ent.bank_id = gam.bank_id;
execute immediate 'truncate table itcustadm.GL_DTPJ_TEST2';
insert into GL_DTPJ_TEST2
(rule_no,
posted_by_user_id,
transaction_id,
transaction_sr_no,
dr_amount,
cr_amount,
tran_crncy_code,
bkdt_tran_flg,
bank_desc
)
select
tq.rule_no,
tq.posted_by_user_id,
tq.transaction_id,
tq.transaction_sr_no,
tq.dr_amount,
tq.cr_amount,
tq.tran_crncy_code,
tq.bkdt_tran_flg,
bank_desc_temp;
end;
When you say "not allowed" what do you mean? Did you get an error?
I ask, because subqueries are definitely allowed inside an insert as select statement, providing you have the syntax correct (and the subquery returns at most one row), e.g.:
create table test_tab (col1 number, col2 varchar2(10));
begin
insert into test_tab
select 1,
(select 'Yes' from dual d2 where d.dummy = d2.dummy)
from dual d;
commit;
end;
/
select * from test_tab;
COL1 COL2
---------- ----------
1 Yes
There are some syntax issues with the code you provided - where is the from clause, and where are the tq and gam aliases defined?
There are two syntax you can use in your insert statement:
(I)
INSERT INTO table_name( column1, column2....columnN)
VALUES ( value1, value2....valueN);
(II)
INSERT INTO table (column1, column2, ... )
SELECT expression1, expression2, ...
FROM source_table(s)
WHERE conditions;
In your example, you should choose the second approach:
insert into GL_DTPJ_TEST2 (rule_no,
posted_by_user_id,
transaction_id,
transaction_sr_no,
dr_amount,
cr_amount,
tran_crncy_code,
bkdt_tran_flg,
bank_desc
)
select tq.rule_no,
tq.posted_by_user_id,
tq.transaction_id,
tq.transaction_sr_no,
tq.dr_amount,
tq.cr_amount,
tq.tran_crncy_code,
tq.bkdt_tran_flg,
ent.bank_desc
from crmuser.gam
join crmuser.end ent
on ent.bank_id = gam.bank_id
;
basically, if you want to add records using an insert statement, you should use a full select statement first. Here is how I would do it:
(1)
select *
from table1;
(2)
select column1
,column2
,column3
from table1;
(3)
select t1.column1
,t1.column2
,t1.column3
,t2.column4
,t2.column5
from table1 t1
join table2 t2
on t2.id = t1.id
;
(4)
insert into table3 (col1
,col2
,col3
,col4
,col5)
select t1.column1
,t1.column2
,t1.column3
,t2.column4
,t2.column5
from table1 t1
join table2 t2
on t2.id = t1.id
;
My database has a lot of tables. How can I display all the table names along with the count of column names in each table?
myoutput:
------------
table_name count(*)
---------- --------
table_t1 12
x_a 5
Y_k 23
samptabl 0
Use USER_TAB_COLS view to get the column_count.
SELECT table_name, count(*) column_count
FROM user_tab_cols
GROUP BY table_name;
If you want the name of the table with the number of columns in it, use DBA's answer here.
If you want name of the table and the number of rows in it, use the following:
SELECT table_name, num_rows
FROM user_tables;
The numbers of rows in this query represent the numbers when the table was last analyzed. To return the latest numbers run ANALYSE tablename before running this query.
If you want to know all table_names and columns count in your Entire Database then here is the query.
Query : SELECT TABLE_NAME,COUNT(COLUMN_NAME) as No_Of_Cols
FROM ALL_TAB_COLS
GROUP BY TABLE_NAME;
Thanks,
Venu.
SELECT table_name, count(*) column_count
FROM all_tables
GROUP BY table_name;
My code is clear enough to describe what i am trying to achieve
SELECT (select column_name from user_tab_cols where table_name='tbl1'
intersect
select column_name from user_tab_cols where table_name='tbl2')
FROM tbl2;
It is throwing ORA-01427: single-row subquery returns more than one row
I understand this error but don't know the alternate solution to achieve my goal .
You don't need the subquery here. Try this instead:
SELECT column_name FROM user_tab_cols WHERE table_name = 'tbl1'
INTERSECT SELECT column_name FROM user_tab_cols WHERE table_name = 'tbl2'
This will return a list of column names that exist in both tbl1 and tbl2.