I am having difficulties setting up a loop in Oracle. I have a table where values are stored for several days. Now I want to get the average of these values for each day.
I was attempting to set up a loop like this:
DECLARE
BEGIN
For iDay in 01.03.20, 02.03.20, 03.03.20
LOOP
SELECT
avg(values)
FROM
table
WHERE
date = 'iDay'
END LOOP;
END
You can simply get the average value using the following query:
SELECT DATE,
AVG (values)
FROM table
WHERE DATE BETWEEN DATE '2020-03-01' AND DATE '2020-03-03';
Or if you want to use the loop then use the query in FOR loop IN clause as follows:
SQL> DECLARE
2 BEGIN
3 FOR DATAS IN (
4 SELECT DATE '2020-03-01' + LEVEL - 1 DT
5 FROM DUAL CONNECT BY
6 LEVEL <= DATE '2020-03-03' - DATE '2020-03-01' + 1
7 ) LOOP
8 DBMS_OUTPUT.PUT_LINE(DATAS.DT);
9 -- YOUR_CODE_HERE
10 END LOOP;
11 END;
12 /
01-MAR-20
02-MAR-20
03-MAR-20
PL/SQL procedure successfully completed.
SQL>
One option would be using Dynamic Query within PL/SQL :
SQL> SET SERVEROUTPUT ON;
SQL> DECLARE
v_result NUMBER;
BEGIN
For iDay in 0..2
LOOP
EXECUTE IMMEDIATE 'SELECT AVG(values) FROM mytable WHERE mydate = :i_Day '
INTO v_result;
USING iDay + date'2020-03-01';
DBMS_OUTPUT.PUT_LINE( v_result );
END LOOP;
END;
/
Why not simply
SELECT "date", avg(values)
FROM "table"
WHERE "date" between DATE '2020-03-01' and DATE '2020-03-03'
GROUP by "date";
Note, date and table are reserved words, most likely the query will without quotes.
Related
i want to call the procedure through anon block like
begin t_maha_del_22_06_p('22.06.2020');end;
but i run it once and want call with loop to take a large date time
like from first 1-st to 15-th august. How can i do it ?
create table t_maha_delete_22_06
(dt date,text varchar2(100));
create or replace procedure my_sch.t_maha_del_22_06_p(p_dt in date default trunc(sysdate) -1) as
begin
delete from t_maha_delete_22_06
where trunc(dt) = p_dt;
commit;
insert into t_maha_delete_22_06
select
trunc(p_dt) dt,
'blablabla' text from dual
commit;
end;
You can do it in loop as follows:
begin
For dt in (select date '2020-08-01' + level - 1 as dates
From dual
Connect by level <= date '2020-08-15' - date '2020-08-01')
Loop
t_maha_del_22_06_p(dt.dates);
End loop;
end;
/
I would like to write a PL/SQL Code to display dates of the same type to add and display as a single date(MyDate Column) and the amount column should add up
Example Input Table Data:
MyDate Amount
4/12/2019 1000
5/12/2019 2000
4/12/2019 3000
Output
MyDate Amount
4/12/2019 4000
5/12/2019 2000
The condition is aggregate function cannot be used.Please guide me
You don't have to use PL/SQL for this. A simple query can be done.
SELECT MyDate, SUM(Amount)
FROM your_table
GROUP BY MyDate
ORDER BY MyDate ASC
Update:
Since you can't use aggregate functions try:
DECLARE
amount NUMBER := 0;
BEGIN
FOR date_cursor IN (
SELECT distinct(MyDate) MyDate
FROM your_table
ORDER BY date_c ASC
) LOOP
FOR amount_cursor IN (
SELECT Amount
FROM your_table
WHERE MyDate = date_cursor.MyDate
) LOOP
amount := amount + amount_cursor.amount;
END LOOP;
dbms_output.put_line('MyDate: ' || date_cursor.MyDate);
dbms_output.put_line('Amount: ' || amount);
amount := 0;
END LOOP;
END;
Here's a dynamic SQL example, just for amusement:
SQL> alter session set nls_date_format = 'dd.mm.yyyy';
Session altered.
SQL> select * From test order by mydate;
MYDATE AMOUNT
---------- ----------
04.12.2019 1000
04.12.2019 3000
05.12.2019 2000
05.12.2019 -5000
SQL> declare
2 l_sum number;
3 begin
4 for cur_r in (select mydate,
5 listagg(amount, '+') within group (order by null) l_str
6 from test
7 group by mydate
8 )
9 loop
10 execute immediate 'select ' || cur_r.l_str ||' from dual' into l_sum;
11 dbms_output.put_line(to_char(cur_r.mydate, 'dd.mm.yyyy') ||': '|| l_sum);
12 end loop;
13 end;
14 /
04.12.2019: 4000
05.12.2019: -3000
PL/SQL procedure successfully completed.
SQL>
Yes, it has its limitations (hint: listagg), but - should be OK for homework purposes.
If we have a column in a table of type number, how can we store the result of select query on that column in an array ?
This sample uses a list (table of numbers) to achieve this, because i find
those lists much more handy:
CREATE OR REPLACE TYPE numberlist AS TABLE OF NUMBER;
DECLARE
v_numberlist numberlist;
BEGIN
SELECT intval numbercolumn
BULK COLLECT INTO v_numberlist
FROM lookup;
FOR i IN 1..v_numberlist.count
LOOP
dbms_output.put_line( v_numberlist(i) );
END LOOP;
END;
Create a type which store number:-
CREATE OR REPLACE TYPE varray is table of number;
--write your select query inside for loop () where i am extracting through level
declare
p varray := varray();
BEGIN
for i in (select level from dual connect by level <= 10) loop
p.extend;
p(p.count) := i.level;
end loop;
for xarr in (select column_value from table(cast(p as varray))) loop
dbms_output.put_line(xarr.column_value);
end loop;
END;
output:-
1
2
3
4
5
6
7
8
9
10
Just an option to use some native SQL datatype. Hope it helps.
SET SERVEROUTPUT ON;
DECLARE
lv_num_tab DBMS_SQL.NUMBER_TABLE;
BEGIN
SELECT LEVEL BULK COLLECT INTO lv_num_tab FROM DUAL CONNECT BY LEVEL < 10;
FOR I IN lv_num_tab.FIRST..lv_num_tab.LAST
LOOP
dbms_output.put_line(lv_num_tab(i));
END LOOP;
END;
You may also want to put the whole select in a table. You can use a BULK COLLECT to an array:
CREATE OR REPLACE TYPE t_my_list AS TABLE OF VARCHAR2(100);
CREATE OR REPLACE
PROCEDURE get_tables(p_owner in varchar2)
as
v_res t_my_list;
v_qry varchar2(4000) := '';
begin
v_qry := ' SELECT table_name from all_tables where owner='''||p_owner||'''';
dbms_output.put_line(v_qry);
-- all at once in the table
execute immediate v_qry bulk collect into v_res;
FOR I in 1..v_res.count
loop
dbms_output.put_line(v_res(i));
end loop;
exception
when others then
raise;
end get_tables;
/
begin
get_tables('E') ;
end;
/
I have a table name SAMPLETABLE this has the tablenames of the tables I require in column TABLENAMES. Lets say the tablenames are TABLEA, TABLEB and TABLEC.
On query
SELECT TABLENAMES FROM SAMPLETABLE WHERE ROWNUM = 1
I get the output the output of TABLENAMES column with TABLEA value.
My problem is, now I want to use this selected value in a select statement. That is,
SELECT * FROM (SELECT TABLENAMES FROM SAMPLETABLE WHERE ROWNUM = 1)
My idea is that it'd return the contents of TABLEA because when the nested SELECT returns TABLEA, the outer SELECT should capture and display it.
On the contrary, I get the output only of the inner statement, that is,
SELECT TABLENAMES FROM SAMPLETABLE WHERE ROWNUM = 1
and
SELECT * FROM (SELECT TABLENAMES FROM SAMPLETABLE WHERE ROWNUM = 1)
return the same output.
I want the first SELECT statement to fetch the returned value of second SELECT and display the table. They above query doesn't do that, so how do I do it? And what is wrong with my idea?
I am on Oracle 10g, any help appreciated.
As table name is not known at compile time you need to use dynamic SQL(execute immediate, native dynamic SQL, for instance) to be able to select from a table, name of which is stored as a string literal - you cannot accomplish it with static SQL
Here is an example:
-- table which contains names of other tables
-- in the table_name column
SQL> create table Table_Names as
2 select 'employees' as table_name
3 from dual
4 ;
Table created
SQL> set serveroutput on;
-- example of an anonymous PL/SQL block
-- where native dynamic SQL (execute immediate statement)
-- is used to execute a dynamically formed select statement
SQL> declare
2 type T_record is record( -- example of record for fetched data
3 f_name varchar2(123),
4 l_name varchar2(123)
5 );
6
7 l_table_name varchar2(123); -- variable that will contain table name
8 l_select varchar2(201);
9 l_record T_Record; -- record we are going to fetch data into
10 begin
11 select table_name
12 into l_table_name -- querying a name of a table
13 from table_names -- and storing it in the l_table_name variable
14 where rownum = 1;
15
16 l_select := 'select first_name, last_name from ' ||
17 dbms_assert.simple_sql_name(l_table_name) ||
18 ' where rownum = 1'; -- forming a query
19
20 execute immediate l_select -- executing the query
21 into l_record;
22 -- simple output of data just for the sake of demonstration
23 dbms_output.put_line('First_name: ' || l_record.f_name || chr(10) ||
24 'Last name: ' || l_record.l_name);
25 exception
26 when no_data_found
27 then dbms_output.put_line('Nothing is found');
28 end;
29 /
First_name: Steven
Last name: King
PL/SQL procedure successfully completed
As a second option you could use weakly typed cursors - refcursors to execute a dynamically formed select statement:
SQL> variable refcur refcursor;
SQL> declare
2 l_table_name varchar2(123);
3 l_select varchar2(201);
4 begin
5 select table_name
6 into l_table_name
7 from table_names
8 where rownum = 1;
9
10 l_select := 'select first_name, last_name from ' ||
11 dbms_assert.simple_sql_name(l_table_name) ||
12 ' where rownum = 1';
13
14 open :refcur
15 for l_select;
16
17 exception
18 when no_data_found
19 then dbms_output.put_line('Nothing is found');
20 end;
21 /
PL/SQL procedure successfully completed.
SQL> print refcur;
FIRST_NAME LAST_NAME
-------------------- -------------------------
Steven King
SQL> spool off;
Find out more about cursors and cursor variables
You can do this with help of dynamic sql. Since the table name is obtained during run time you have to frame the query dynamically and run it.
Declare
Tab_Name Varchar2(30);
Begin
SELECT TABLENAMES into Tab_Name FROM SAMPLETABLE WHERE ROWNUM = 1;
Execute Immediate 'Select * into (Collection Variable) from ' || Tab_Name;
End
/
I just gave it as example. You declare a variable to get the data out or something else as you need. But when you try to use execute immediate with input parameter read about sql injection and then write your code.
I need to create a Oracle tables with random number of columns for load testing. I just want to specify number of columns with type NUMBER, number of columns with type VARCHAR2 etc and the fields should be generated automatically. Also, I will be filling up the tables with random data for which I will be using dbms_random.
How can I achieve this?
"I just want to specify number of
columns with type NUMBER, number of
columns with type VARCHAR2 etc and the
fields should be generated
automatically."
The following procedure does just that. Note that it is rather basic; you might want to make it more sophisticated, for example by varying the length of the varchar2 columns:
SQL> create or replace procedure bld_table
2 ( p_tab_name in varchar2
3 , no_of_num_cols in pls_integer
4 , no_of_var_cols in pls_integer
5 , no_of_date_cols in pls_integer
6 )
7 as
8 begin
9 execute immediate 'create table '||p_tab_name||' ('
10 ||' pk_col number not null'
11 ||', constraint '||p_tab_name||'_pk primary key (pk_col) using index)';
12 << numcols >>
13 for i in 1..no_of_num_cols loop
14 execute immediate 'alter table '||p_tab_name||' add '
15 ||' col_n'||trim(to_char(i))||' number';
16 end loop numcols;
17 << varcols >>
18 for i in 1..no_of_var_cols loop
19 execute immediate 'alter table '||p_tab_name||' add '
20 ||' col_v'||trim(to_char(i))||' varchar2(30)';
21 end loop varcols;
22 << datcols >>
23 for i in 1..no_of_date_cols loop
24 execute immediate 'alter table '||p_tab_name||' add '
25 ||' col_d'||trim(to_char(i))||' date';
26 end loop datcols;
27 end bld_table;
28 /
Procedure created.
SQL>
Here it is in action:
SQL> exec bld_table ('T23', 2, 3, 0)
PL/SQL procedure successfully completed.
SQL> desc t23
Name Null? Type
----------------------------------------- -------- ----------------------------
PK_COL NOT NULL NUMBER
COL_N1 NUMBER
COL_N2 NUMBER
COL_V1 VARCHAR2(30 CHAR)
COL_V2 VARCHAR2(30 CHAR)
COL_V3 VARCHAR2(30 CHAR)
SQL>
We can also use dynamic SQL to populate the table with rows of random data.
SQL> create or replace procedure pop_table
2 ( p_tab_name in varchar2
3 , p_no_of_rows in pls_integer
4 )
5 as
6 stmt varchar2(32767);
7 begin
8 stmt := 'insert into '||p_tab_name
9 || ' select rownum ';
10 for r in ( select column_name
11 , data_type
12 , data_length
13 from user_tab_columns
14 where table_name = p_tab_name
15 and column_name != 'PK_COL' )
16 loop
17 case r.data_type
18 when 'VARCHAR2' then
19 stmt := stmt ||', dbms_random.string(''a'', '||r.data_length||')';
20 when 'NUMBER' then
21 stmt := stmt ||', dbms_random.value(0, 1000)';
22 when 'DATE' then
23 stmt := stmt ||', sysdate + dbms_random.value(-1000, 0)';
24 end case;
25 end loop;
26 stmt := stmt || ' from dual connect by level <= '||p_no_of_rows;
27 execute immediate stmt;
28 end pop_table;
29 /
Procedure created.
SQL>
Note that the primary key is populated with the ROWNUM so it will most likely fail if the table already contains rows.
SQL> exec pop_table('T23', 4)
PL/SQL procedure successfully completed.
SQL> select * from t23
2 /
PK_COL COL_N1 COL_N2 COL_V1 COL_V2 COL_V3
---------- ---------- ---------- ------------------------------ ----------------------------- ------------------------------
1 913.797432 934.265814 NUtxjLoRQMCTLNMPKVGbTZwJeYaqnXTkCcWu WFRSHjXdLfpgVYOjzrGrtUoX jIBSoYOhSdhRFeEeFlpAxoanPabvwK
2 346.879815 104.800387 NTkvIlKeJWybCTNEdvsqJOKyidNkjgngwRNN PPIOInbzInrsVTmFYcDvwygr RyKFoMoSiWTmjTqRBCqDxApIIrctPu
3 93.1220275 649.335267 NTUxzPRrKKfFncWaeuzuyWzapmzEGtAwpnjj jHILMWJlcMjnlboOQEIDFTBG JRozyOpWkfmrQJfbiiNaOnSXxIzuHk
4 806.709357 857.489387 ZwLLkyINrVeCkUpznVdTHTdHZnuFzfPJbxCB HnoaErdzIHXlddOPETzzkFQk dXWTTgDsIeasNHSPbAsDRIUEyPILDT
4 rows selected.
SQL>
Again, there are all sorts of ways to improve the sophistication of the data.
As an aside, using these sorts of data pools for load testing is not always a good idea. Performance problems are often caused by skews in the distribution of data values which you just aren't going to get with DBMS_RANDOM. This is particularly true of some date columns - e.g. START_DATE - which would tend to be clustered together in real life but the above procedure will not generate that pattern. Similarly maxing out the varchar2 columns will lead to tables which take up more storage than they wlll under real-life usage.
In short, randomly generated data is better than nothing but we need to understand its weaknesses.
Two approaches
1) Write code to generate text files containing the CREATE TABLE commands that you need to run and populate your tables, then execute these using SQL*Plus.
2) Use Dynamic SQL embedded inside PL/SQL -
PROCEDURE create_random_table
(pTableName IN VARCHAR2,
pNumberOfColumns IN INTEGER)
IS
PRAGMA AUTONOMOUS_TRANSACTION;
lCommand VARCHAR2(32000);
BEGIN
lCommand :=
'CREATE TABLE '||pTableName||'(';
FOR i IN 1..pNumberOfColumns LOOP
append your column definition here
END LOOP;
lCommand := lCommand||';';
--
EXECUTE IMMEDIATE lCommand;
END;
You could also use 'CREATE TABLE AS SELECT' to populate your table at the same time (see other answer).
This should give you a good starting point - there isn't anything in the system that will do what you want without writing code.
You may generate such table by yourself.
Create table with required datatypes:
Create Table RandomTable
AS
Select dbms_random.string('A', 1) CharField,
dbms_random.string('a', 20) VarCharField,
TRUNC(dbms_random.value(0, 35000)) IntField,
dbms_random.value(0, 35000) NumberField,
Level SequenceField,
sysdate + dbms_random.value(-3500, 3500) DateField
from dual connect by level < 1000
(You can change 1000 to required rows numbers, and add required data types)
After that you can create or populate tables with random data from RandomTable
Create Table TestTable1
AS
SELECT CharField as a, NumberField as b
from RandomTable
INSERT INTO TestTable2(DateFrom, Quantity)
SELECT DateField, IntField
from RandomTable
Where SequenceField <= 500