I'm currently writing a script which will allow me to input a file (generally .sql) and it'll generate a list of every table that's used in that file. the process is simple as it opened the input file, checks for a substring and if that substring exists outputs the line to the screen.
the substring that being checked is tsql keywords that is indicative of a selected table such as INTO, FROM and JOIN. not being a T-SQL wizard those 3 keywords are the only ones i know of that are used to select a table in a query.
So my question is, in T-SQL are INTO, FROM an JOIN the only ways to get a table? or are these others?
There're many ways to get a table, here're some of them:
DELETE
FROM
INTO
JOIN
MERGE
OBJECT_ID (N'dbo.mytable', N'U') where U is the object type for table.
TABLE, e.g. ALTER TABLE, TRUNCATE TABLE, DROP TABLE
UPDATE
However, by using your script, you'll not only get real tables, but maybe VIEW and temporary table. Here're 2 examples:
-- Example 1
SELECT *
FROM dbo.myview
-- Example 2
WITH tmptable AS
(
SELECT *
FROM mytable
)
SELECT *
FROM tmptable
Related
So I have a query that shows a huge amount of mutations in postgres. The quality of data is bad and i have "cleaned" it as much as possible.
To make my report so user-friendly as possible I want to filter out some rows that I know the customer don't need.
I have following columns id, change_type, atr, module, value_old and value_new
For change_type = update i always want to show every row.
For the rest of the rows i want to build some kind of logic with a combination of atr and module.
For example if the change_type <> 'update' and concat atr and module is 'weightperson' than i don't want to show that row.
In this case id 3 and 11 are worthless and should not be shown.
Is this the best way to solve this or does anyone have another idea?
select * from t1
where concat(atr,module) not in ('weightperson','floorrentalcontract')
In the end my "not in" part will be filled with over 100 combinations and the query will not look good. Maybe a solution with a cte would make it look prettier and im also concerned about the perfomance..
CREATE TABLE t1(id integer, change_type text, atr text, module text, value_old text, value_new text) ;
INSERT INTO t1 VALUES
(1,'create','id','person',null ,'9'),
(2,'create','username','person',null ,'abc'),
(3,'create','weight','person',null ,'60'),
(4,'update','id','order','4231' ,'4232'),
(5,'update','filename','document','first.jpg' ,'second.jpg'),
(6,'delete','id','rent','12' ,null),
(7,'delete','cost','rent','600' ,null),
(8,'create','id','rentalcontract',null ,'110'),
(9,'create','tenant','rentalcontract',null ,'Jack'),
(10,'create','rent','rentalcontract',null ,'420'),
(11,'create','floor','rentalcontract',null ,'1')
Fiddle
You could put the list of combinations in a separate table and join with that table, or have them listed directly in a with-clause like this:
with combinations_to_remove as (
select *
from (values
('weight', 'person'),
('floor' ,'rentalcontract')
) as t (atr, module)
)
select t1.*
from t1
left join combinations_to_remove using(atr, module)
where combinations_to_remove.atr is null
I guess it would be cleaner and easier to maintain if you put them in a separate table!
Read more on with-queries if that sounds strange to you.
I am looking for some help with trying to link 2 sheets that have a number of Filters that I have setup but are both sitting in separate tables. The reason this is because I have a number of aggregated columns that are different for the 2 tables and want to keep this separately as I will be building more sheets as I go along.
The filters that are the same within the 2 sheets are the following:
we_date
product
manager
patch
Through the data manager I managed to create an association between the 2 tables for we_date but from reading on this site and other searches on Google I can't make any associations between these tables and this is where I am stuck.
The 2 sheets will now allow me to filter using the we_date, but if I use the filters for product, manager or patch then nothing happens on my 2nd sheet as they are not linked.
Currently in my data load editor I have 2 sections of select queries like the following:
Table1
QUALIFY *;
w:
SELECT
*
FROM
table1
;
UNQUALIFY *;
Table2
QUALIFY *;
w_c:
SELECT
*
FROM
table2
;
UNQUALIFY *;
I would really appreciate if somebody could advise a fix on the issue I am having.
In Qlik, field names of identical values from different tables are automatically associated.
When you're calling Qualify *, you're actually renaming all field names and explicitly saying NOT to associate.
Take a look at the Qlik Sense documentation on Qualify *:
The automatic join between fields with the same name in different
tables can be suspended by means of the qualify statement, which
qualifies the field name with its table name. If qualified, the field
name(s) will be renamed when found in a table. The new name will be in
the form of tablename.fieldname. Tablename is equivalent to the label
of the current table, or, if no label exists, to the name appearing
after from in LOAD and SELECT statements.
We can use as to manually reassign field names.
SELECT customer_id, private_info as "private_info_1", favorite_dog from table1;
SELECT customer_id, private_info as "private_info_2", car from table2;
Or, we can correctly use Qualify. Example:
table1 and table2 have a customer_id field, and private_info field. We want customer_id field to be the associative value, and private_info to not be. We would use QUALIFY on private_info, which Qlik would then rename based on file name.
QUALIFY private_info;
SELECT * from table1;
SELECT * from table2;
The following field names would then be: customer_id (associated), and table1.private_info, and table2.private_info
I have a table contains columns 'employeename' and 'id', how can I sort the 'employeename' column following alphabetical order of the names initial?
Say the table is like this now:
employeename rid eid
Dave 1 1
Ben 4 2
Chloe 6 6
I tried the command ORDER BY, it shows what I want but when I query the data again by SELECT, the showed table data is the same as original, indicting ORDER BY does not modify the data, is this correct?
SELECT *
FROM employee
ORDER BY employeename ASC;
I expect the table data to be modified (sorted by names alphabetical order) like this:
employeename rid eid
Ben 4 2
Chloe 6 6
Dave 1 1
the showed table data is the same as original, indicting ORDER BY does not modify the data, is this correct?
Yes, this is correct. A SELECT statement does not change the data in a table. Only UPDATE, DELETE, INSERT or TRUNCATE statements will change the data.
However, your question shows a misconception on how a relational database works.
Rows in a table (of a relational database) are not sorted in any way. You can picture them as balls in a basket.
If you want to display data in a specific sort order, the only (really: the only) way to do that is to use an ORDER BY in your SELECT statement. There is no alternative to that.
Postgres allows to define a VIEW that includes an ORDER BY which might be an acceptable workaround for you:
CREATE VIEW sorted_employee;
AS
SELECT *
FROM employee
ORDER BY employeename ASC;
Then you can simply use
select *
from sorted_employees;
But be aware of the drawbacks. If you run select * from sorted_employees order by id then the data will be sorted twice. Postgres is not smart enough to remove the (useless) order by from the view's definition.
Some related questions:
Default row order in SELECT query - SQL Server 2008 vs SQL 2012
What is the default SQL result sort order with 'select *'?
Is PostgreSQL order fully guaranteed if sorting on a non-unique attribute?
Why do results from a SQL query not come back in the order I expect?
My db tables:
db_1
db_2
db_3
My internal table:
it_comb
it_comb has a structure with some fields from db_1, db_2, db_3.
All db tables have different structures.
I want to select everything from db_1, db_2, db_3 into the correct fields of it_comb with a where condition.
I would like to do something like this: (This doesn't work)
SELECT * From db_1, db_2, db_3 into CORRESPONDING FIELDS OF TABLE it_comb WHERE db_1-MATNR LIKE db_2-MATNR AND db_1-MATNR LIKE db_3-MATNR.
Obviously, this doesn't work because I can't use ',' like that. How do I write this in ABAP? So that it_comb is filled with data from db_1, db_2 and db_3.
Another problem is that every time I select something into it_comb, my previous data gets overwritten.
Code example would be appreciated for ABAP-Beginner.
You can use inner join -
SELECT * APPENDING CORRESPONDING FIELDS OF TABLE it_comb
FROM db_1 AS a
INNER JOIN db_2 AS b
ON a~matnr = b~matnr
INNER JOIN db_3 AS c
ON a~matnr = c~matnr
WHERE (Your any other condition).
APPENDING won't overwrite the previous record from internal table it_comb.
Warning: Use APPENDING if internal table is TYPE STANDARD otherwise you'll get dump.
Also check the SELECT - JOIN documentaion
One other thing you can do in the newer ABAP versions is
select * from mara inner join mvke on mvke~matnr = mara~matnr into table #data(lt_combined).
loop at lt_combined into data(ls_combined).
write: / ls_combined-mara-matnr, ls_combined-mvke-vkorg.
endloop.
this will define and populate your internal table in one step without the need for a separate "data" statement.
Note that in a join with *, you will get an internal table with substructures based on the table names -- since the structure is implied in the field-list of the select, you can also do something like this for a more efficient database query (so it doesn't need to return all the fields) which also eliminates the substructures:
select mara~matnr, mvke~vkorg from mara inner join mvke on mvke~matnr = mara~matnr into table #data(lt_combined).
loop at lt_combined into data(ls_combined).
write: / ls_combined-matnr, ls_combined-vkorg.
endloop.
Hope this helps!
Without JOIN I executed SELECT statements one by one as follows
data it_comb type TABLE OF vbak.
select * APPENDING CORRESPONDING FIELDS OF TABLE it_comb FROM vbak UP TO 10 ROWS.
select * APPENDING CORRESPONDING FIELDS OF TABLE it_comb FROM vbrk UP TO 10 ROWS.
select * APPENDING CORRESPONDING FIELDS OF TABLE it_comb FROM likp UP TO 10 ROWS.
I don't understand why the following doesn't fail. How does the subquery have access to a column from a different table at the higher level?
drop table if exists temp_a;
create temp table temp_a as
(
select 1 as col_a
);
drop table if exists temp_b;
create temp table temp_b as
(
select 2 as col_b
);
select col_a from temp_a where col_a in (select col_a from temp_b);
/*why doesn't this fail?*/
The following fail, as I would expect them to.
select col_a from temp_b;
/*ERROR: column "col_a" does not exist*/
select * from temp_a cross join (select col_a from temp_b) as sq;
/*ERROR: column "col_a" does not exist
*HINT: There is a column named "col_a" in table "temp_a", but it cannot be referenced from this part of the query.*/
I know about the LATERAL keyword (link, link) but I'm not using LATERAL here. Also, this query succeeds even in pre-9.3 versions of Postgres (when the LATERAL keyword was introduced.)
Here's a sqlfiddle: http://sqlfiddle.com/#!10/09f62/5/0
Thank you for any insights.
Although this feature might be confusing, without it, several types of queries would be more difficult, slower, or impossible to write in sql. This feature is called a "correlated subquery" and the correlation can serve a similar function as a join.
For example: Consider this statement
select first_name, last_name from users u
where exists (select * from orders o where o.user_id=u.user_id)
Now this query will get the names of all the users who have ever placed an order. Now, I know, you can get that info using a join to the orders table, but you'd also have to use a "distinct", which would internally require a sort and would likely perform a tad worse than this query. You could also produce a similar query with a group by.
Here's a better example that's pretty practical, and not just for performance reasons. Suppose you want to delete all users who have no orders and no tickets.
delete from users u where
not exists (select * from orders o where o.user_d = u.user_id)
and not exists (select * from tickets t where t.user_id=u.ticket_id)
One very important thing to note is that you should fully qualify or alias your table names when doing this or you might wind up with a typo that completely messes up the query and silently "just works" while returning bad data.
The following is an example of what NOT to do.
select * from users
where exists (select * from product where last_updated_by=user_id)
This looks just fine until you look at the tables and realize that the table "product" has no "last_updated_by" field and the user table does, which returns the wrong data. Add the alias and the query will fail because no "last_updated_by" column exists in product.
I hope this has given you some examples that show you how to use this feature. I use them all the time in update and delete statements (as well as in selects-- but I find an absolute need for them in updates and deletes often)