Im using a DB2 Database. What would be a suitable SQL query to find out if a column is exists in a table or list of tables?
e.g
if "column_name" is found in "table name" or [list of table names]
return true or the name of tables that have that column.
Many thanks.
Tested on DB2 z/OS 9.1 and LUW 9.7:
SELECT STRIP(TBCREATOR) || '.' || STRIP(TBNAME)
FROM SYSIBM.SYSCOLUMNS
WHERE NAME = 'your_col'
AND TBNAME IN ('list', 'of', 'tables')
If you only want results from a specific schema you might add AND TBCREATOR = 'your_schema' to the end of the query.
Use SYSCAT.COLUMNS catalog view:
SELECT TABNAME
FROM SYSCAT.COLUMNS
WHERE
TABNAME IN ('table name 1', 'table name 2') AND
COLNAME = 'column_name';
Another way to do this is with error handling:
declare v_sql varchar(1000);
declare col_missing integer default 0;
declare col_does_not_exist condition for sqlstate '42703';
declare continue handler for col_does_not_exist set col_missing = 1;
set v_sql = 'select table.foo from table';
execute immediate v_sql;
if col_missing = 1 then
--Do something if column foo doesn't exist.
end if;
This method will work on session tables, and you can also use it on an object even if you don't know whether it is a table, view, alias, etc.
It is important to specify table.foo rather than just the column name, as otherwise the existence of another object (such as a variable) called foo would break the test.
This continue handler will mask any other errors for columns missing within the scope, so it is best to limit the scope to just the test you want to do.
Related
I would be interested to drop all tables in a Redshift schema. Even though this solution works
DROP SCHEMA public CASCADE;
CREATE SCHEMA public;
is NOT good for me since that it drops SCHEMA permissions as well.
A solution like
DO $$ DECLARE
r RECORD;
BEGIN
-- if the schema you operate on is not "current", you will want to
-- replace current_schema() in query with 'schematodeletetablesfrom'
-- *and* update the generate 'DROP...' accordingly.
FOR r IN (SELECT tablename FROM pg_tables WHERE schemaname = current_schema()) LOOP
EXECUTE 'DROP TABLE IF EXISTS ' || quote_ident(r.tablename) || ' CASCADE';
END LOOP;
END $$;
as reported in this thread How can I drop all the tables in a PostgreSQL database?
would be ideal. Unfortunately it doesn't work on Redshift (apparently there is no support for for loops).
Is there any other solution to achieve it?
Run this SQL and copy+paste the result on your SQL client.
If you want to do it programmatically you need to built little bit code around it.
SELECT 'DROP TABLE IF EXISTS ' || tablename || ' CASCADE;'
FROM pg_tables
WHERE schemaname = '<your_schema>'
I solved it through a procedure that deletes all records. Using this technique to truncate fails but deleting it works fine for my intents and purposes.
create or replace procedure sp_truncate_dwh() as $$
DECLARE
tables RECORD;
BEGIN
FOR tables in SELECT tablename
FROM pg_tables
WHERE schemaname = 'dwh'
order by tablename
LOOP
EXECUTE 'delete from dwh.' || quote_ident(tables.tablename) ;
END LOOP;
RETURN;
END;
$$ LANGUAGE plpgsql;
--call sp_truncate_dwh()
In addition to demircioglu's answer, I had to add Commit after every drop statement to drop all tables in my schema. SELECT 'DROP TABLE IF EXISTS ' || tablename || ' CASCADE; COMMIT;' FROM pg_tables WHERE schemaname = '<your_schema>'
P.S.: I do not have required reputation to add this note as a comment and had to add as an answer.
Using Python and pyscopg2 locally on my PC I came up with this script to delete all tables in schema:
import psycopg2
schema = "schema_to_be_deleted"
try:
conn = psycopg2.connect("dbname='{}' port='{}' host='{}' user='{}' password='{}'".format("DB_NAME", "DB_PORT", "DB_HOST", "DB_USER", "DB_PWD"))
cursor = conn.cursor()
cursor.execute("SELECT tablename FROM pg_tables WHERE schemaname = '%s'" % schema)
rows = cursor.fetchall()
for row in rows:
cursor.execute("DROP TABLE {}.{}".format(schema, row[0]))
cursor.close()
conn.commit()
except psycopg2.DatabaseError as error:
logger.error(error)
finally:
if conn is not None:
conn.close()
Replace correctly values for DB_NAME, DB_PORT, DB_HOST, DB_USER and DB_PWD to connect to the Redshift DB
The following recipe differs from other answers in the regard that it generates one SQL statement for all tables we're going to delete.
SELECT
'DROP TABLE ' ||
LISTAGG("table", ', ') ||
';'
FROM
svv_table_info
WHERE
"table" LIKE 'staging_%';
Example result:
DROP TABLE staging_077815128468462e9de8ca6fec22f284, staging_abc, staging_123;
As in other answers, you will need to copy the generated SQL and execute it separately.
References
|| operator concatenates strings
LISTAGG function concatenates every table name into a string with a separator
The table svv_table_info is used because LISTAGG doesn't want to work with pg_tables for me. Complaint:
One or more of the used functions must be applied on at least one user created tables. Examples of user table only functions are LISTAGG, MEDIAN, PERCENTILE_CONT, etc
UPD. I just now noticed that SVV_TABLE_INFO page says:
The SVV_TABLE_INFO view doesn't return any information for empty tables.
...which means empty tables will not be in the list returned by this query. I usually delete transient tables to save disk space, so this does not bother me much; but in general this factor should be considered.
My goal is pretty straightforward - if table has rows, drop it.
Despite the fact that currently there are several similar answers none of them worked for me.
DB2 Drop table if exists equivalent
Suggested solution:
IF EXISTS (SELECT name FROM sysibm.systables WHERE name = 'mylib.mytable') THEN
DROP TABLE mylib.mytable;END IF;
Result:
SQL State: 42601 Vendor Code: -199 Message: [SQL0199] Keyword IF not expected.
Valid tokens: ( CL END GET SET CALL DROP FREE HOLD LOCK OPEN WITH ALTER BEGIN
Drop DB2 table if exists
Suggested solution:
--#SET TERMINATOR #
begin
declare statement varchar(128);
declare continue handle for sqlstate '42710' BEGIN END;
SET STATEMENT = 'DROP TABLE MYLIB.MYTABLE';
EXECUTE IMMEDIATE STATEMENT;
end #
Result:
Message: [SQL0104] Token HANDLE was not invalid. Valid tokens: HANDLER or, if replace handle with handler:
Message: [SQL0199] Keyword STATEMENT not expected. Valid tokens: SQL PATH RESULT SCHEMA CURRENT CONNECTION DESCRIPTOR.
From answer about views
Suggested solution:
DROP TABLE MY_TABLE ONLY IF EXISTS source.
Result:
Message: [SQL0104] Token ONLY was not invalid. Valid tokens: RESTRICT CASCADE
So, I wonder if an alternate solution exists. CL solution is also interesting.
I'm assuming you may want to do this more than once, so a procedure might be in order.
CREATE or replace PROCEDURE DROP_LIVE_TABLE
(in #table varchar(10)
,in #library varchar(10)
)
BEGIN
declare #stmt varchar(100);
declare #cnt int;
IF exists( select * from systables
where sys_dname = #library
and sys_tname = #table
and table_type in ('P','T')
) THEN
SELECT int(sum(number_rows))
INTO #cnt
from SYSTABLESTAT
where sys_dname = #library
and sys_tname = #table
;
IF #cnt > 0 THEN
set #stmt = 'DROP TABLE '||#library||'.'||#table||' CASCADE';
execute immediate #stmt;
END IF;
END IF;
RETURN;
END;
The CASCADE keyword causes any dependent objects such as indexes, logical files, views, or such to be deleted as well.
Here is a CL answer to this question:
PGM PARM(&FILENAME)
DCL VAR(&FILENAME) TYPE(*CHAR) LEN(10)
DCL VAR(&NUMRECS) TYPE(*DEC) LEN(10 0)
RTVMBRD FILE(&FILENAME) NBRCURRCD(&NUMRECS)
IF COND(&NUMRECS > 0) THEN(DLTF +
FILE(&FILENAME))
OUT: ENDPGM
This solution would have trouble if the physical file has dependencies such as indexes or logical files. Those dependencies would have to be deleted first.
The solution by #danny117 on the other hand does not work in all environments. For example I was unable to coerce it to work in SQuirreL client. But it does work in i Navigator. It also works in RUNSQLSTM, but I was unable to determine how to make it work with unqualified table references. If the tables are unqualified, RUNSQLSTM uses the default collection from DFTRDBCOL. The CURRENT_SCHEMA special register does not return the value from DFTRDBCOL.
Here is the if table has rows drop it solution using a compound statement:
begin
if( exists(
select 1 from qsys2.systables
where table_schema = 'MYLIB'
and table_name = 'MYTABLE'
)) then
if( exists(
select 1 from mylib.mytable
)) then
drop table mylib.mytable;
end if;
end if;
end;
I am guessing at the reason you would want to do this, but if it is to allow creation of a new table, then best way may be with a CREATE OR REPLACE TABLE if you are at IBM i v7.2 or greater.
If all you want to do is make sure you have an empty table, TRUNCATE (v7.2+) or DELETE may be better options.
Drop table if exists using atomic statement.
BEGIN ATOMIC
IF( EXISTS(
SELECT 1 FROM TABLES
WHERE TABLE_SCHEMA = 'MYLIB'
AND TABLE_NAME = 'MYTABLE'
)) THEN
DROP TABLE MYLIB/MYTABLE;
END IF;
END;
try this:
BEGIN
IF EXISTS (SELECT NAME FROM QSYS2.SYSTABLES WHERE TABLE_SCHEMA = 'YOURLIBINUPPER' AND TABLE_NAME = 'YOURTABLEINUPPER') THEN
DROP TABLE YOURLIB.YOURTABLE;
END IF;
END ;
I'm using Firebird 2.5.0. I know a value and need to find all tables, columns in which it occurs.
I created procedure:
CREATE OR ALTER PROCEDURE NEW_PROCEDURE (
searching_value varchar(30))
returns (
table_with_value varchar(100),
column_with_value varchar(100))
as
declare variable all_tables varchar(50);
declare variable all_columns varchar(50);
declare variable all_values varchar(50);
begin
FOR SELECT
r.rdb$relation_name, f.rdb$field_name
from rdb$relation_fields f
join rdb$relations r on f.rdb$relation_name = r.rdb$relation_name
and r.rdb$view_blr is null
and (r.rdb$system_flag is null or r.rdb$system_flag = 0)
order by 1, f.rdb$field_position INTO :all_tables, :all_columns
DO
BEGIN
FOR SELECT all_columns FROM all_tables
INTO :all_Values
DO
BEGIN
IF (SEARCHING_VALUE = all_Values) THEN
BEGIN
table_With_Value = all_Tables;
column_With_Value = all_Columns;
SUSPEND;
END
END
END
END^
When I run it I get error message:
Undefined name.
Dynamic SQL Error.
SQL error code = -204.
Table unknown.
ALL_TABLES.
At line 21, column 13.
So in this select statement "SELECT all_columns FROM all_tables" it is not taking values from previous for select statement but just trying to find table all_tables. How to fix it?
The problem is that all_columns is considered to be a colum name and all_tables a table name and not your variables in:
SELECT all_columns FROM all_tables
You can't parametrize objectnames in a query like this. Also note that if it had been possible to parametrize object names, you would have had to use :all_columns and :all_tables for disambiguation.
Instead you will need to create a dynamic SQL statement and execute that with EXECUTE STATEMENT (or more specifically: FOR EXECUTE STATEMENT).
In this case:
FOR EXECUTE STATEMENT 'SELECT "' || all_columns || '" FROM "' || all_tables || '"'
INTO :all_values
DO
BEGIN
/* .... */
END
I have quoted the object names to account for case sensitive column and table names (or identifiers that are invalid unquoted). Constructing a query like this might leave you open to SQL injection if the values are obtained from another source than the Firebird metadata tables.
I have some big tables (30+ columns) with NOT NULL constraints. I would like to change all those constraints to NULL. To do it for a single column I can use
ALTER TABLE <your table> MODIFY <column name> NULL;
Is there a way to do it for all columns in one request ? Or should I copy/paste this line for all columns (><) ?
Is there a way to do it for all columns in one request ?
Yes. By (ab)using EXECUTE IMMEDIATE in PL/SQL. Loop through all the columns by querying USER_TAB_COLUMNS view.
For example,
FOR i IN
( SELECT * FROM user_tab_columns WHERE table_name = '<TABLE_NAME>' AND NULLABLE='N'
)
LOOP
EXECUTE IMMEDIATE 'ALTER TABLE <TABLE_NAME> MODIFY i.COLUMN_NAME NULL';
END LOOP;
In my opinion, by the time you would write the PL/SQL block, you could do it much quickly by using a good text editor. In pure SQL you just need 30 queries for 30 columns.
For a single table you can issue a single alter table command to set the listed columns to allow null, which is a little more efficient than running one at a time, but you still have to list every column.
alter table ...
modify (
col1 null,
col1 null,
col3 null);
If you were applying not null constraints then this would be more worthwhile, as they require a scan of the table to ensure that no nulls are present, and (I think) an exclusive table lock.
You can query user_tab_cols and combine it with a FOR cursor & EXECUTE IMMEDIATE to modify all not null columns - the PL/SQL block for doing like that would look like so:
DECLARE
v_sql_statement VARCHAR2(2000);
BEGIN
FOR table_recs IN (SELECT table_name, column_name
FROM user_tab_cols
WHERE nullable = 'N') LOOP
v_sql_statement :=
'ALTER TABLE ' || table_recs.table_name || ' MODIFY ' || table_recs.column_name || ' NULL';
EXECUTE IMMEDIATE v_sql_statement;
END LOOP;
END;
If you want to do it for all columns in a database instead of the ones in current schema, you can replace user_tab_cols and put in dba_tab_cols; I'd just run the query in the FOR to ensure that the columns being fetched are indeed the correct ones to be modified
I have the following table name template, there are a couple with the same name and a number at the end: fmj.backup_semaforo_geo_THENUMBER, for example:
select * from fmj.backup_semaforo_geo_06391442
select * from fmj.backup_semaforo_geo_06398164
...
Lets say I need to select a column from every table which succeeds with the 'fmj.backup_semaforo_geo_%' filter, I tried this:
SELECT calle --This column is from the backup_semaforo_geo_# tables
FROM (SELECT table_name
FROM all_tables
WHERE owner = 'FMJ' AND table_name LIKE 'BACKUP_SEMAFORO_GEO_%');
But I'm getting the all_tables tables name data:
TABLE_NAME
----------
BACKUP_SEMAFORO_GEO_06391442
BACKUP_SEMAFORO_GEO_06398164
...
How can I achieve that without getting the all_tables output?
Thanks.
Presumably your current query is getting ORA-00904: "CALLE": invalid identifier, because the subquery doesn't have a column called CALLE. You can't provide a table name to a query at runtime like that, unfortunately, and have to resort to dynamic SQL.
Something like this will loop through all the tables and for each one will get all the values of CALLE from each one, which you can then loop through. I've used DBMS_OUTPUT to display them, assuming you're doing this in SQL*Plus or something that can deal with that; but you may want to do something else with them.
set serveroutput on
declare
-- declare a local collection type we can use for bulk collect; use any table
-- that has the column, or if there isn't a stable one use the actual data
-- type, varchar2(30) or whatever is appropriate
type t_values is table of table.calle%type;
-- declare an instance of that type
l_values t_values;
-- declare a cursor to generate the dynamic SQL; where this is done is a
-- matter of taste (can use 'open x for select ...', then fetch, etc.)
-- If you run the query on its own you'll see the individual selects from
-- all the tables
cursor c1 is
select table_name,
'select calle from ' || owner ||'.'|| table_name as query
from all_tables
where owner = 'FMJ'
and table_name like 'BACKUP_SEMAFORO_GEO%'
order by table_name;
begin
-- loop around all the dynamic queries from the cursor
for r1 in c1 loop
-- for each one, execute it as dynamic SQL, with a bulk collect into
-- the collection type created above
execute immediate r1.query bulk collect into l_values;
-- loop around all the elements in the collection, and print each one
for i in 1..l_values.count loop
dbms_output.put_line(r1.table_name ||': ' || l_values(i));
end loop;
end loop;
end;
/
May be a dynamic SQL in a PLSQL program;
for a in (SELECT table_name
FROM all_tables
WHERE owner = 'FMJ' AND table_name LIKE 'BACKUP_SEMAFORO_GEO_%')
LOOP
sql_stmt := ' SELECT calle FROM' || a.table_name;
EXECUTE IMMEDIATE sql_stmt;
...
...
END LOOP;