Why does this PL/SQL not find a table? - oracle

Question

I have 2 table DOQUANGDUC1 and DOQUANGDUC, in table DOQUANGDUC list table in database I need check:
declare
BEGIN
FOR x IN (select table_name,column_name from DOQUANGDUC) LOOP
INSERT INTO DOQUANGDUC1 (table_name,column_name)
SELECT count(x.column_name),column_name FROM x.table_name GROUP BY column_name having count(x.column_name) >2;
END LOOP;
END;
I run sql error
Error at line 1
ORA-06550: line 9, column 57:
PL/SQL: ORA-00942: table or view does not exist
ORA-06550: line 8, column 10:
PL/SQL: SQL Statement ignored
I am sure two table already use.

Answer 1

PL/SQL: ORA-00942: table or view does not exist
The cause of the error message is this line:
FROM x.table_name
This is telling Oracle to query a table called table_name in a schema called X and that does not exist. Hence the failure.
I think what you're trying to do is loop through a list of tables and columns and count how many values each column has, and insert the results into another table. You can't do that with pure SQL, you need to use dynamic SQL to format the statement.
declare
stmt varchar2(32767);
begin
for x in (select table_name, column_name from doquangduc) loop
stmt := 'insert into doquangduc1(table_name, column_name, col_count) '
||' select '''||x.table_name||''', '''||x.column_name||''', count('||x.column_name||') '
||' from '||x.table_name
||' having count('||x.column_name||') > 2';
execute immediate stmt;
end loop;
end;
/
Here is a working demo on db<>fiddle.
Note that I have changed the insert statement to populate three columns in doquangduc1: correct this to fit your actual table structure (which you haven't posted).
It seems that the CMS_CIF_MUREX_NAME table has 292 records I add 1 duplicate record when running your command it shows the result column col_count = 293
My interpretation of your requirement is to count how many rows are populated for each column. Maybe that is not your actual requirement. Such misunderstandings are always a risk when you post a piece of code and expect us to reverse engineer your business logic. It is easier if you tell us what you're actually trying to achieve.
If you want counts for each distinct value in the column you can add a GROUP clause before the HAVING clause in my query.
'group by '||x.column_name ||
You may also want to add the value to the records inserted into doquangduc1, so you know which value has which count.

Answer 2

Approaches to Inserting into a Table through an Implicit Cursor or a Select Statement
Our Requirement:
We are going through the records in doquangduc and finding instances where the column_name appears more than twice.
Next, we are placing these records in another table, doquangduc1, while preserving the counts (placing them in doquangduc1).
Ultimately, these records are needed so they can be viewed.
Comments about this requirement:
It is not really clear that we really need to perform a transformation of the table, doquangduc, and then insert into another table to view the resulting records. This answer assumes this is necessary.
We create and execute DDL for tables needed first.
CREATE TABLE doquangduc
AS
SELECT
table_name,
column_name
FROM
user_tab_columns;
We create the table, doquangduc1, and make sure there is a column called col_count:
CREATE TABLE doquangduc1
AS
SELECT
table_name,
column_name,
1 col_count
FROM
user_tab_columns
WHERE
table_name IS NULL;
We sort through the doquangduc table to identify scenarios you have identified.
BEGIN
FOR x IN (
WITH qry AS (
SELECT
table_name,
column_name,
COUNT(1)
OVER(PARTITION BY column_name) AS col_count
FROM
user_tab_columns
)
SELECT
table_name,
column_name,
col_count
FROM
qry
WHERE
col_count > 2
) LOOP
INSERT INTO doquangduc1 (
table_name,
column_name,
col_count
) VALUES (
x.table_name,
x.column_name,
x.col_count
);
END LOOP;
END;
As various people have commented, do we really need an implicit cursor to perform this insert into the table, doquangduc1, so that we can view the results?
We could just perform a INSERT INTO with a SELECT statement to more efficiently insert these records into doquangduc1:
INSERT INTO doquangduc1
WITH qry AS (
SELECT
table_name,
column_name,
COUNT(1)
OVER(PARTITION BY column_name) AS col_count
FROM
user_tab_columns
)
SELECT
table_name,
column_name,
col_count
FROM
qry
WHERE
col_count > 2;