I have 3 textfields where user types table name and 2 column names which need to be merged.
How should I merge (combine) 2 column values into 1?
I use oracle 11g enterprise
concatenate?
select col1 || ' ' || col2 from tablex
This is a very vague requirement. Concatenate the values maybe?
insert into sometable( Column1 )
values ( Column1 || Column2 );
If you need to specify the table name to INSERT into, then you will need to use dynamic SQL to achieve this. Would you need to specify the target column name as well? This example assumes you would use PL/SQL, which may not be appropriate in your case.
sql_stmt := 'INSERT INTO '|| specified_table || '(' || merge_column || ') VALUES ( :1 )';
EXECUTE IMMEDIATE sql_stmt USING column1 || column2;
http://docs.oracle.com/cd/B13789_01/appdev.101/b10807/13_elems017.htm
You could make another column (an auxiliary column ) and replace the other 2 columns with this one.
Merging columns in Oracle Live
SELECT CONCAT (ENAME, JOB) from scott.EMP
the above command will merge ENAME and JOB columns, and these 2 different columns will be shown in a single column
Related
I am trying to loop through 5 tables all with a similar naming format. I am able to return the tables names by using the query
select table_name from all tables
where table_name like '
order by table_name
My intention is to insert the data from all the 5 tables into one table where a particular date condition is met. I know I can do this via union all but this makes my script very long as I have to paste the same script for 5 tables, I was wondering if there is a way to do without using union all but rather using dynamic sql? I am new to dynamic sql.
It might look like this:
begin
for cur_r in (select table_name
from all_tables
where table_name like 'ABC%'
)
loop
execute immediate
'insert into target_table (id, name, address) ' ||
'select id, name, address from ' || cur_r.table_name ||
' where date_column = ' || trunc(sysdate);
end loop;
end;
/
loop through all_tables, fetching only those you're interested in
compose insert statement, presuming that all tables (from previous step) share the same set of common columns
include where clause, if you want
Assume following table named t1:
create table t1(
clid number,
A number,
B number,
C number
)
insert into t1 values(1, 1, 1, 1);
insert into t1 values(2, 0, 1, 0);
insert into t1 values(3, 1, 0, 1);
clid A B C
1 1 1 1
2 0 1 0
3 1 0 1
Type of columns A, B, and C is number. What I need to do is to change types of those columns to VARCHAR but in a quite tricky way.
In my real table I need to change datatype for hundred of columns so it is not so convenient to write a statement like following hundred of time:
ALTER TABLE table_name
MODIFY column_name datatype;
What i need to do is rather to convert all columns to VARCHAR except CLID column like we can do that in Python or R
Is there any way to do so in Oracle SQL or PLSQL?
Appreciate your help.
Here is a example of procedure that can help...
It accepts two parameters that should be a name of your table and list of columns you do not want to change...
At the begining there is a cursor that gets all the column names for your table except the one that you do not want to change...
Then it loop's though the columns and changes them...
CREATE OR REPLACE procedure test_proc(p_tab_name in varchar2
, p_col_names in varchar2)
IS
v_string varchar2(4000);
cursor c_tab_cols
is
SELECT column_name
FROM ALL_TAB_COLS
WHERE table_name = upper(p_tab_name)
and column_name not in (select regexp_substr(p_col_names,'[^,]+', 1, level) from dual
connect by regexp_substr(p_col_names, '[^,]+', 1, level) is not null);
begin
FOR i_record IN c_tab_cols
loop
v_string := 'alter table ' || p_tab_name || ' modify '
|| i_record.column_name || ' varchar(30)';
EXECUTE IMMEDIATE v_string;
end loop;
end;
/
Here is a demo:
DEMO
You can also extend this procedure with a type of data you want to change into... and with some more options I am sure....
Unfortunately, that isn't as simple as you'd want it to be. It is not a problem to write query which will write query for you (by querying USER_TAB_COLUMNS), but - column must be empty in order to change its datatype:
SQL> create table t1 (a number);
Table created.
SQL> insert into t1 values (1);
1 row created.
SQL> alter table t1 modify a varchar2(1);
alter table t1 modify a varchar2(1)
*
ERROR at line 1:
ORA-01439: column to be modified must be empty to change datatype
SQL>
If there are hundreds of columns involved, maybe you can't even
create additional columns in the same table (of VARCHAR2 datatype)
move values in there
drop "original" columns
rename "new" columns to "old names"
because there'a limit of 1000 columns per table.
Therefore,
creating a new table (with appropriate columns' datatypes),
moving data over there,
dropping the "original" table
renaming the "new" table to "old name"
is probably what you'll finally do. Note that it won't be necessarily easy either, especially if there are foreign keys involved.
A "query that writes query for you" might look like this (Scott's sample tables):
SQL> SELECT 'insert into dept (deptno, dname, loc) '
2 || 'select '
3 || LISTAGG ('to_char(' || column_name || ')', ', ')
4 WITHIN GROUP (ORDER BY column_name)
5 || ' from emp'
6 FROM user_tab_columns
7 WHERE table_name = 'EMP'
8 AND COLUMN_ID <= 3
9 /
insert into dept (deptno, dname, loc) select to_char(EMPNO), to_char(ENAME), to_char(JOB) from emp
SQL>
It'll save you from typing names of hundreds of columns.
I think its not possible to change data type of a column if values are there...
Empty the column by copying values to a dummy column and change data types.
I have a problem in that I want my output to be a single table (lets call it Output) with 2 columns: one for the "TableName" and one for the DateTime of the last update (using the scn_to_timestamp(max(ora_rowscn)) command).
I have 100 tables and I want to pull in the last update date/times for all these tables into the Output table.
So I can do this:
insert into Output(TableName)
select table_name
from all_tables;
which will put all the tables I have from my database into the TableName column. But I don't know how to loop through each entry and use the tablename as a variable and pass this into the scn_to_timestamp(ora_rowscn).
I thought I would try something like below:
for counter in Output(TableName) LOOP
insert into Output(UpdateDate)
select scn_to_timestamp(max(ora_rowscn))
from counter;
END LOOP;
Any suggestions?
Thank you
This query is a little bit clumsy as it uses xmlgen to execute dynamic sql in a query, but it might work for you.
select x.*
from all_tables t,
xmltable('/ROWSET/ROW' passing
dbms_xmlgen.getxmltype('select ''' || t.table_name ||
''' tab_name, max(ora_rowscn) as la from ' ||
t.table_name)
COLUMNS tab_name varchar2(30) PATH 'TAB_NAME',
max_scn number PATH 'LA') x
Here is a sqlfiddle demo
You can also use PLSQL and then use execute immediate
I have many columns in oracle database and some new are added with values. I like to find out which columns have values other than 0 or null. So I am looking for column names for which some sort of useful values exists at least in one row.
How do I do this?
Update: This sounds very close. How do I modify this to suit my needs?
select column_name, nullable, num_distinct, num_nulls
from all_tab_columns
where table_name = 'SOME_TABLE'
You can query all the columns using the dba_tab_cols view and then see if there are columns which have values other than 0 or null.
create or replace function f_has_null_rows(
i_table_name in dba_tab_cols.table_name%type,
i_column_name in dba_tab_cols.table_name%type
) return number is
v_sql varchar2(200);
v_count number;
begin
v_sql := 'select count(*) from ' || i_table_name ||
' where ' || i_column_name ' || ' is not null and '
|| i_column_name || ' <>0 ';
execute immediate v_sql into v_count;
return v_count;
end;
/
select table_name, column_name from dba_tab_Cols
where f_has_null_rows (table_name, column_name) > 0
If you have synonyms in some schemas, you mighty find some of the tables are repeated. You'll have to change the code to cater to that.
Also, the check "is not equal to zero" might not be valid for columns that are not integers and will give errors if columns are of date datatype. You'll need to add the conditions for those cases. use the Data_type column in dba_tab_cols and add the condition as needed.
Select Column_name
from user_tab_columns
where table_name='EMP' and num_nulls=0;
This finds columns which does not have any values so you can perform any actions to that.
Sorry, I misread the question the first time.
From this post on Oracle's forums
Assuming your stats are up to date:
SELECT t.table_name,
t.column_name
FROM user_tab_columns t
WHERE t.nullable = 'Y'
AND t.num_distinct = 0;
Will return you a list of table names and columns that are null. You might want to add something like:
AND t.table_name = upper('Your_table_name')
in there to limit the results to just your table.
select 'cats' as mycolumname from T
where exists (Select id from T where cats is not null)
union
select 'dogs' as mycolumnname from T
where exists (select id from T where dogs is not null)
# ad nauseam
is how to do it in SQL. EDIT: Different flavors of SQL might let you optimize with LIMIT or TOP 'n' in the subquery. Or maybe they're even smart enough to realize that EXIST() only needs one row and optimize silently/transparently. P.S. Add your test for zero to the subquery.
I need remove the quotes from the names of the columns in many tables in my schema. there is any way to automate this process?, any function in oracle or some tool that allows me to change the names of the columns removing the quotes. I am using oracle 11g.
UPDATE
I'm sorry, I had to rephrase my question.
thanks in advance.
I assume here by "fields" you mean "column names".
Keep in mind that column names in Oracle are not case sensitive unless you put them in quotes when creating the table. It's generally not a good idea to use quotes around the column names when creating the table. In other words, if you create the table like this:
CREATE TABLE FOO (
colUMN1 varchar2(10),
CoLumn2 number(38)
)
Then you can still run select statements like this:
SELECT column1, column2 FROM FOO
You can also do this:
SELECT COLUMN1, COLUMN2 FROM FOO
Also note that if you run this query, you'll see that Oracle stored the column names as uppercase in the data dictionary:
SELECT * FROM ALL_TAB_COLUMNS WHERE TABLE_NAME = 'FOO'
So there's no need to rename these columns to all uppercase. The queries you write can use all uppercase column names (assuming the tables weren't created using quotes around the column names) and they'll work fine. It's generally a bad idea to try to force them to be case sensitive.
If you just want to get rid of all the case sensitive column names
SQL> create table foo ( "x" number );
Table created.
SQL> ed
Wrote file afiedt.buf
1 begin
2 for x in (select *
3 from user_tab_cols
4 where column_name != UPPER(column_name))
5 loop
6 execute immediate 'ALTER TABLE ' || x.table_name ||
7 ' RENAME column "' || x.column_name || '"' ||
8 ' TO ' || upper(x.column_name);
9 end loop;
10* end;
SQL> /
PL/SQL procedure successfully completed.
SQL> desc foo
Name Null? Type
----------------------------------------- -------- ----------------------------
X NUMBER