I have this migration script;
ALTER TABLE table_name MODIFY (column_name NULL);
How do I make it idempotent?
Either you can use an exception handler:
DECLARE
CANNOT_MODIFIY_TO_NULL EXCEPTION;
PRAGMA EXCEPTION_INIT(CANNOT_MODIFIY_TO_NULL, -1451);
BEGIN
EXECUTE IMMEDIATE 'ALTER TABLE TABLE_NAME MODIFY (column_name NULL)';
exception
when CANNOT_MODIFIY_TO_NULL then
NULL;
END;
or check NULLABLE in view USER_TAB_COLUMNS:
DECLARE
CURSOR Cols IS
SELECT COLUMN_NAME
FROM USER_TAB_COLUMNS
WHERE TABLE_NAME = 'TABLE_NAME'
AND NULLABLE = 'N'
AND COLUMN_NAME = 'COLUMN_NAME';
BEGIN
FOR aCol IN Cols LOOP
EXECUTE IMMEDIATE 'ALTER TABLE TABLE_NAME MODIFY ('||aCol.COLUMN_NAME||' NULL)';
END LOOP;
END;
Related
I am new to Oracle, I am trying to write a procedure in Oracle to delete foreign key constraints for a table. I have already done this for MySQL and its working. I am not sure with the syntax, apologies for that, but my query is working If I run it individually. I want to do the same thing(removing foreign key constraints) for multiple tables and don't want to write queries multiple times. hence first I am finding the foreign keys associated with that table , storing them in cursor and later removing all of the foreign keys by creating and executing drop constraints query associated with that table. following code is giving multiple errors to me.
CREATE OR REPLACE PROCEDURE removeConstraintsForTable(vTableName IN varchar2) IS
BEGIN
cName VARCHAR(2048);
sql_stmt VARCHAR2(2048);
CURSOR cur IS
SELECT DISTINCT CONSTRAINT_NAME
FROM ALL_CONSTRAINTS WHERE OWNER= sys_context('userenv','current_schema')
AND TABLE_NAME = vTableName AND CONSTRAINT_TYPE='R';
BEGIN
OPEN cur;
LOOP
FETCH cur INTO cName;
EXIT WHEN cur%notfound;
sql_stmt := CONCAT(CONCAT(CONCAT('ALTER TABLE ',vTableName),CONCAT(' DROP FOREIGN KEY ',cName)),';');
SELECT sql_stmt FROM dual;
INSERT INTO TEMP(Name) VALUES(sql_stmt);
COMMIT;
END LOOP;
END
/
CALL removeConstraintsForTable('table1');
CALL removeConstraintsForTable('table2');
CALL removeConstraintsForTable('table3');
CALL removeConstraintsForTable('table4');
COMMIT;
You have an extra BEGIN right at the start of your procedure, and the final END is missing a semicolon. You shouldn't really be using VARCHAR, and you could declare the cName variable using the data dictionary anyway; however an implicit loop will be simpler, as will using the concatenation operator || instead of nested CONCAT() calls, and the generated statement should not end in a semicolon:
create or replace procedure removeconstraintsfortable(p_table_name in varchar2) is
sql_stmt varchar2(2048);
begin
for rec in (
select owner, constraint_name
from all_constraints
where owner = sys_context('userenv','current_schema')
and table_name = p_table_name
and constraint_type = 'R'
)
loop
sql_stmt := 'ALTER TABLE "' || rec.owner || '"."' || p_table_name || '"'
|| ' DROP CONSTRAINT "' || rec.constraint_name || '"';
insert into temp(name) values(sql_stmt);
end loop;
commit;
end;
/
As pointed out in comments, the generated statement should be drop constraint.
I'm not sure why you're inserting into a table or where you execute the statement, but you can do it all in one if you prefer:
create or replace procedure removeconstraintsfortable(p_table_name in varchar2) is
sql_stmt varchar2(2048);
begin
for rec in (
select owner, constraint_name
from all_constraints
where owner = sys_context('userenv','current_schema')
and table_name = p_table_name
and constraint_type = 'R'
)
loop
sql_stmt := 'ALTER TABLE "' || rec.owner || '"."' || p_table_name || '"'
|| ' DROP CONSTRAINT "' || rec.constraint_name || '"';
dbms_output.put_line(sql_stmt);
execute immediate sql_stmt;
end loop;
end;
/
The dbms_output call just shows you the generated statement(s), before execute immediate executes it, well, immediately.
Quick demo; very basic table set-up:
create table t42 (id number primary key);
create table t43 (id number references t42 (id));
select table_name, constraint_name, constraint_type
from all_constraints
where table_name in ('T42', 'T43');
TABLE_NAME CONSTRAINT_NAME C
------------------------------ ------------------------------ -
T43 SYS_C00138153 R
T42 SYS_C00138152 P
Then call the procedure which shows the generated statement:
set serveroutput on
exec removeConstraintsForTable('T43');
ALTER TABLE "STACKOVERFLOW"."T43" DROP CONSTRAINT "SYS_C00138153"
PL/SQL procedure successfully completed.
and then check the constraint has gone:
select table_name, constraint_name, constraint_type
from all_constraints
where table_name in ('T42', 'T43');
TABLE_NAME CONSTRAINT_NAME C
------------------------------ ------------------------------ -
T42 SYS_C00138152 P
I fixed a number of syntax issues for you. Try this.
CREATE OR REPLACE PROCEDURE removeConstraintsForTable(vTableName IN varchar2) IS
cName VARCHAR2(30); -- identifiers are max 30 chars
sql_stmt VARCHAR2(2048);
CURSOR cur IS
SELECT DISTINCT CONSTRAINT_NAME
FROM USER_CONSTRAINTS
WHERE TABLE_NAME = vTableName AND CONSTRAINT_TYPE='R';
BEGIN
OPEN cur;
LOOP
FETCH cur INTO cName;
EXIT WHEN cur%notfound;
sql_stmt := 'ALTER TABLE ' || vTableName || ' DROP CONSTRAINT ' || cName;
INSERT INTO RANGERADMIN1.TEMP(Name) VALUES(sql_stmt);
END LOOP;
COMMIT;
END removeConstraintsForTable;
/
call removeConstraintsForTable('table1');
call removeConstraintsForTable('table2');
call removeConstraintsForTable('table3');
call removeConstraintsForTable('table4');
-- COMMIT; -- not necessary
I've number of tables that i want to drop some columns and add some another columns again. (oracle database)
All of tables are empty.
does it work??
DECLARE
CURSOR cursor_name
IS
SELECT TABLE_NAME
FROM SYS.ALL_TABLES
WHERE OWNER = 'username';
TN NVARCHAR2 (30);
TABLE_COUNT NUMBER (3);
TCDROP NVARCHAR2 (1000);
TCADD NVARCHAR2 (1000);
BEGIN
SELECT COUNT (1)
INTO TABLE_COUNT
FROM SYS.ALL_TABLES
WHERE OWNER = 'username';
OPEN cursor_name;
FOR i IN 1 .. TABLE_COUNT
LOOP
FETCH cursor_name INTO TN;
TCDROP := 'ALTER TABLE ' || TN || ' DROP (*columns list*);';
EXECUTE IMMEDIATE TCDROP;
TCADD :=
'ALTER TABLE ' || TN || ' ADD (*columns and datatype list*);';
EXECUTE IMMEDIATE TCADD;
EXIT WHEN cursor_name%NOTFOUND;
END LOOP;
CLOSE cursor_name;
END;
/
Yes, this will certainly work. I'd recommend to put in the owner/schema of the tables, though. Besides, it is unusual or unsafe to query the number of tables and the loop through the list. I'd put it in a simple for loop:
DECLARE
stmt VARCHAR2(1000);
BEGIN
FOR t IN (SELECT table_name FROM all_tables WHERE owner='XYZ') LOOP
stmt := 'ALTER TABLE '||owner||'.'||table_name||' DROP (*columns list*);';
DBMS_OUTPUT.PUT_LINE(stmt);
EXECUTE IMMEDIATE (stmt);
stmt:= 'ALTER TABLE '||owner||'.'||table_name||' ADD (*columns and datatype list*);';
DBMS_OUTPUT.PUT_LINE(stmt);
EXECUTE IMMEDIATE (stmt);
END LOOP;
END;
/
I want Stored Procedure which create Temporary table using Create Table ... Select ... Statement.
And then select the records from same created table.
And finally drop that created table...
I want all these functionality in same stored procedure.
I have create the following stored procedure. But i got the below error
PL/SQL: ORA-00942: table or view does not exist
This one is my Procedure
DECLARE
TEMP_TBL VARCHAR2(4000);
TBL_NAME VARCHAR2(200) := 'ABC_TEST';
BEGIN
TEMP_TBL := 'CREATE TABLE MY_TAB_COL AS(SELECT TABLE_NAME,COLUMN_NAME,DATA_TYPE,to_lob(DATA_DEFAULT) AS DATA_DEFAULT,NULLABLE FROM ALL_TAB_COLS WHERE TABLE_NAME=''' || TBL_NAME || ''')';
DBMS_OUTPUT.PUT_LINE(TEMP_TBL);
EXECUTE IMMEDIATE TEMP_TBL;
FOR DD_COLUMNS IN
(SELECT TABLE_NAME FROM MY_TAB_COL)
LOOP
DBMS_OUTPUT.PUT_LINE('DD_COLUMNS.TABLE_NAME');
END LOOP;
END;
I'm not sure why you want scenario like that, and not reccomend to use this code in production. I'm pretty sure in the 99% of the cases, this approach can be written in other way. But you can try the code bellow(Everything in your procedure should use dynamic sql)
declare
TBL_NAME varchar2(200) := 'ABC_TEST';
lv_Sql varchar2(4000);
begin
lv_Sql := 'CREATE TABLE MY_TAB_COL AS(SELECT TABLE_NAME,COLUMN_NAME,DATA_TYPE,to_lob(DATA_DEFAULT) AS DATA_DEFAULT,NULLABLE FROM ALL_TAB_COLS WHERE TABLE_NAME=''' ||
TBL_NAME || ''')';
DBMS_OUTPUT.PUT_LINE(lv_Sql);
execute immediate lv_Sql;
lv_Sql := 'begin
for DD_COLUMNS in (select TABLE_NAME from MY_TAB_COL) loop
DBMS_OUTPUT.PUT_LINE(DD_COLUMNS.TABLE_NAME);
end loop;
end;';
DBMS_OUTPUT.PUT_LINE(lv_Sql);
execute immediate lv_Sql;
for R in (select *
from user_objects
where object_name = 'MY_TAB_COL'
and object_type = 'TABLE') loop
DBMS_OUTPUT.PUT_LINE('drop table ' || R.Object_Name);
execute immediate 'drop table ' || R.Object_Name;
end loop;
end;
I need to drop an Oracle table only if it 1) exists AND 2) Is NOT Empty
I wrote this code but if the table does not exist the code does not work:
DECLARE
rec_cnt1 NUMBER :=0;
rec_cnt2 NUMBER :=0;
BEGIN
SELECT COUNT(*) INTO rec_cnt1 FROM ALL_TABLES WHERE TABLE_NAME = 'MyTable';
SELECT num_rows INTO rec_cnt2 FROM USER_TABLES WHERE TABLE_NAME = 'MyTable';
IF rec_cnt1 = 1 THEN
BEGIN
IF rec_cnt2 < 1 THEN
EXECUTE IMMEDIATE 'DROP TABLE MyTable cascade constraints';
END IF;
END;
END IF;
END;
/
What am I doing wrong? Please help.
Many thanks in advance
If you want to drop a table if it exists and empty(as the title of the question states) you could do this as follows:
create or replace procedure DropTableIfEmpty(p_tab_name varchar2)
is
l_tab_not_exists exception;
pragma exception_init(l_tab_not_exists, -942);
l_is_empty number;
l_query varchar2(1000);
l_table_name varchar2(32);
begin
l_table_name := dbms_assert.simple_sql_name(p_tab_name);
l_query := 'select count(*)
from ' || l_table_name ||
' where rownum = 1';
execute immediate l_query
into l_is_empty;
if l_is_empty = 0
then
execute immediate 'drop table ' || l_table_name;
dbms_output.put_line('Table "'|| p_tab_name ||'" has been dropped');
else
dbms_output.put_line('Table "'|| p_tab_name ||'" exists and is not empty');
end if;
exception
when l_tab_not_exists
then dbms_output.put_line('Table "'|| p_tab_name ||'" does not exist');
end;
When you are trying to drop a table, or query a table, which does not exist, Oracle will raise ORA-00942 exception and execution of a pl/sql block halts. We use pragma exception_init statement to associate ORA-00942 exception with our locally defined exception l_tab_not_exists in order to handle it appropriately.
Test case:
SQL> exec droptableifempty('tb_test'); -- tb_test table does not exists
Table "tb_test" does not exist
SQL> create table tb_test(
2 col number
3 );
table TB_TEST created.
SQL> exec droptableifempty('tb_test');
Table "tb_test" has been dropped
As a side note. Before querying num_rows column of [dba][all][user]_tables in order to determine number of rows a table has, you need to gather table statistic by executing dbms_stats.gather_table_stats(user, '<<table_name>>');, otherwise you wont get the actual number of rows.
In PL/SQL it is 'normal' to catch the exception.
If it is the correct exception then continue with the next part of your code.
DECLARE
rec_cnt1 NUMBER :=0;
rec_cnt2 NUMBER :=0;
BEGIN
SELECT COUNT(*) INTO rec_cnt1 FROM ALL_TABLES WHERE TABLE_NAME = 'MyTable';
SELECT num_rows INTO rec_cnt2 FROM USER_TABLES WHERE TABLE_NAME = 'MyTable';
IF rec_cnt1 = 1 THEN
BEGIN
IF rec_cnt2 < 1 THEN
EXECUTE IMMEDIATE 'DROP TABLE MyTable cascade constraints';
END IF;
END;
END IF;
EXCEPTION
DBMS_OUTPUT.PUT_LINE('OH DEAR AN EXCEPTION WAS THROWN DUE TO' || SQLERRM);
DBMS_OUTPUT.PUT_LINE('THE ORACLE CODE IS ' || SQLCODE);
-- if it is the oracle code for no such table, or no data selected
-- everything is fine.
END;
Of course it won't work if the table doesn't exist. Your second select would get a "No data found" exception, and you're not doing any exception handling. At least you should move the second select inside the first IF block. Best to add exception handling.
here is an easy way to solve this problem:
BEGIN
EXECUTE IMMEDIATE 'DROP TABLE [sssss]';
EXCEPTION WHEN OTHERS THEN NULL;
END;
I need to drop a table and make a new one. If I drop the table and the table doesn't exist, I get an error
How can I check if the table exists?
I'm working on Oracle 11g
Thanks in advance.
You could do something like this:
DECLARE v_exist PLS_INTEGER;
BEGIN
SELECT COUNT(*) INTO v_exist
FROM user_tables
WHERE table_name = 'YOURTABLEHERE';
IF v_exist = 1 THEN
EXECUTE IMMEDIATE 'DROP TABLE YOURTABLEHERE';
END IF;
DECLARE
eTABLE_OR_VIEW_DOES_NOT_EXIST EXCEPTION;
PRAGMA EXCEPTION_INIT(eTABLE_OR_VIEW_DOES_NOT_EXIST, -942);
BEGIN
EXECUTE IMMEDIATE 'DROP TABLE SCHEMA.WHATEVER';
EXCEPTION
WHEN eTABLE_OR_VIEW_DOES_NOT_EXIST THEN
NULL;
END;
Share and enjoy.
something like
select count(*) from user_tables
where table_name= :table name
or
select count(*) from dba_tables
where owner = :table owner
and table_name = :table name
or a heavy-handed alternative:
begin execute immediate 'drop table table_name';
exception when others then null;
end;
I have been using the following procedure to take care of this:
create or replace procedure drop_table_if_exists ( p_table_name varchar2 )
is
it_exist number;
begin
select count(*)
into it_exists
from user_tables
where table_name = p_table_name
;
if it_exists >= 1 then
execute immediate 'drop table '||p_table_name;
end if;
end;
/
exec drop_table_if_exists ( 'TABLE_TO_DROP' );