If I have table 1 called "FILES" and table 2 called "Networks" and the value that goes in FILES.Network_ID must be from a list defined in Networks.Network_ID
If I wanted to run a query to find out if there are any values under network_id in table 1 that are not defined in table 2, I tried the below which doesn't work apparently...Also, I'm using the SQL view of MS ACCESS
SELECT *
FROM (FILES f LEFT JOIN Networks
ON f.Network_ID <> Networks.Network_ID)
This query won't work properly because your are trying to join if the ids don't match, so ideally while making join the rows will match
For instance if table Files contains rows with network id 1,2,3 and table Networks contains network id 1,2 then upon joining you will get a combination of rows with network ids [1,2], [2,1],[3,1],[3,2].
Instance if you use a subquery and then filter it using IN clause will work
select * from files where network_id not in (select network_id from networks);
Try this
SELECT *
FROM (FILES f LEFT JOIN Networks
ON f.Network_ID =Networks.Network_ID)
Where Networks.Network_ID Is Null
To ensure data integrity create a relationship between both tables.
Related
When I query I do not get match list side by side and database reference fails, why?
I tried using one connection and two different schemas, first schema name table has same reference details with second table column, and I would like to compare side by side what equals exactly from rw.reference table 1, with table 2 qt.ref_number because they should match between both. I only get output data from top first query with rd.reference and second table does not list anything with, qt.ref_number, why postgresql does not cross database reference?
Query:
Select distinct
rd.reference,
region1_scorecard
From local_dev.user.rawdata rd
Inner join customerid as id
on rd.site=id.site
union all
Select distinct
qt.ref_number,
region2_decision
From local_dev.account.quote qt
Inner join rep_id id
on qt.application=id.application
Order by rd.reference
I'm looking for a solution where a query should return:
a) a limited set of rows when there are rows in the lowest joined table
b) all rows if there is no data in the lowest joined table
c) taking into account that it is possible that there is more than 1 such join
Objective:
we are implementing security using data. Rows from the table (MainTable) are filtered on 1 or more columns. These columns have a relationship with other tables (LookupTable). Security is defined on the LookupTable.
Example1: the MainTable contains contact information. One of the columns holds the country code, this column has a relationship with a LookupTable that contains the country codes. The user can only select a country code that exists in the LookupTable. The security admin can then define that a user can only work with contacts of one or more countries. When that user accesses the MainTable he/she will only get the contacts of that limited list of countries.
Example2: the MainTable contains products. One column holds the country of origin code, another column the product group. Security setup can limit the access to the product MainTable of a user to a list of countries AND a list of product groups.
The security setup works by Management-by-Exception, whichs means that the MainTable is filtered when one or more "security filters" are defined but if no security filters are defined then the user will get ALL rows from MainTable. So my query should return a limited number of rows if any security filter is defined but should return all rows if there are no security filters defined.
Current situation:
I have been working on a query for the case of Example2. There are 4 possible scenarios:
No security filters are defined
expected outcome: all rows are returned
Security filter defined only for first LookupTable
expected outcome: only rows matching values between LookupTable1 and security filter are returned
Security filter defined only for second LookupTable
expected outcome: only rows matching values between LookupTable2 and security filter are returned
Security filter defined only for both LookupTables
expected outcome: only rows matching values between LookupTable1 AND LookupTable2 and security filter are returned
The query I have is correct for cases 2,3 and 4 but fails for case 1 where no rows are returned (as per my understanding this is due to the fact that both JOINS return an empty result set).
Background:
The application provides the (power) users with some kind of table designer which means that they can define which columns are linked to a LookupTable and which of these LookupTables can be used for the "security filters".
This means that, potentially, we could have a MainTable with for example 200 columns of which 20 are linked to a LookupTable which are defined as security filter. The queries are stored procedures which are generated when "design" changes are saved.
With the query I have now (working for 3 out 4 cases) the number of scenarios is equal to 2^N where N is the number of LookupTables. If N is 20 the total goes over 1 million.
Security setup is done with Profiles assigned to Users and Filter Sets assigned to Profiles and Filter Set Entries containing the actual values to filter on (if any).
The environment is currently on MS SQL 2017 but will be put into production on SQL on Azure.
Example of the query (but look further below for the link to dbfiddle):
SELECT E.col_pk, E.col_28, E.col_7, E.col_8, E.col_9, E.col_1052
FROM MainTable AS E
LEFT JOIN LookupTable2 AS L28 ON L28.col_pk = E.col_28
JOIN SecUserProfile AS UP28 ON UP28.IdentityUserId = #UserId
JOIN SecProfileFilterSets AS PFS28 ON PFS28.SecProfileId = UP28.SecProfileId
LEFT JOIN SecFilterSetEntry AS SE28 ON SE28.SecFilterSetId = PFS28.SecFilterSetId AND SE28.MdxEntityId = 2 AND SE28.EntityKey = L28.col_pk
LEFT JOIN LookupTable13 AS L1052 ON L1052.col_pk = E.col_1052
JOIN SecUserProfile AS UP1052 ON UP1052.IdentityUserId = #UserId
JOIN SecProfileFilterSets AS PFS1052 ON PFS1052.SecProfileId = UP1052.SecProfileId
LEFT JOIN SecFilterSetEntry AS SE1052 ON SE1052.SecFilterSetId = PFS1052.SecFilterSetId AND SE1052.MdxEntityId = 13 AND SE1052.EntityKey = L1052.col_pk
WHERE
(SE28.SecFilterSetId IS NOT NULL AND SE1052.SecFilterSetId IS NOT NULL)
OR
(
SE28.SecFilterSetId IS NOT NULL AND
NOT EXISTS
(
SELECT TOP 1 NUP1052.Id FROM SecUserProfile AS NUP1052
JOIN SecProfileFilterSets AS NPFS1052 ON NPFS1052.SecProfileId = NUP1052.SecProfileId
JOIN SecFilterSetEntry AS NSE1052 ON NSE1052.SecFilterSetId = NPFS1052.SecFilterSetId AND NSE1052.MdxEntityId = 13
WHERE NUP1052.IdentityUserId = #UserId
)
)
OR
(
NOT EXISTS
(
SELECT TOP 1 NUP28.Id FROM SecUserProfile AS NUP28
JOIN SecProfileFilterSets AS NPFS28 ON NPFS28.SecProfileId = NUP28.SecProfileId
JOIN SecFilterSetEntry AS NSE28 ON NSE28.SecFilterSetId = NPFS28.SecFilterSetId AND NSE28.MdxEntityId = 2
WHERE NUP28.IdentityUserId = #UserId
)
AND SE1052.SecFilterSetId IS NOT NULL
)
OR
(
NOT EXISTS
(
SELECT TOP 1 NUP28.Id FROM SecUserProfile AS NUP28
JOIN SecProfileFilterSets AS NPFS28 ON NPFS28.SecProfileId = NUP28.SecProfileId
JOIN SecFilterSetEntry AS NSE28 ON NSE28.SecFilterSetId = NPFS28.SecFilterSetId AND NSE28.MdxEntityId = 2
WHERE NUP28.IdentityUserId = #UserId
)
AND
NOT EXISTS
(
SELECT TOP 1 NUP1052.Id FROM SecUserProfile AS NUP1052
JOIN SecProfileFilterSets AS NPFS1052 ON NPFS1052.SecProfileId = NUP1052.SecProfileId
JOIN SecFilterSetEntry AS NSE1052 ON NSE1052.SecFilterSetId = NPFS1052.SecFilterSetId AND NSE1052.MdxEntityId = 13
WHERE NUP1052.IdentityUserId = #UserId
)
)
Issue:
I have the following issues but they probably boil down to 1 in the end:
my current query is only 75% correct
even if my current query is correct it cannot be used in production with the potential high(er) number of lookup tables.
performance needs to be taken into account. Just as we don't know the number of columns and lookup tables at design time we don't know how many rows the tables will contain. The main table may hold 500, 50000 or 500000 records.
In the end all this will boil down to the right solution :)
I think this is not the easiest of questions (otherwise I will feel very stupid) and for those willing to take a look I've prepared a sandbox environment on dbfiddle representing the use-case I'm working with. I've setup the query to run 4 times, once for each of the scenarios.
I have Four tables as follows
Review (REV_ID pk , REV_NAME)
Meeting (MEETING_ID pk,MEETING_NAME,REV_ID fk to Review)
Task (TASK_ID pk,TASK_NAME,REV_ID fk to Review)
Answer (ANS_ID pk,ANS_NAME,REV_ID fk to Review)
Now I want to select a particular Review and want to create a table with
Linked meetings
Linked answers
Linked tasks
How shall I proceed with it?
I tried writing join query but I was only able to get data if Rev_ID is present in all tables?
select * from
(SELECT *
FROM meeting
WHERE EXISTS (SELECT *
FROM review WHERE meeting.rev_id
=review.rev_id)
and meeting.rev_id=142),
(SELECT *
FROM answer
WHERE EXISTS (SELECT *
FROM review WHERE answer.rev_id
=rev.rev_id)
and answer.ans_rev_id=142),
(SELECT *
FROM task
WHERE EXISTS (SELECT *
FROM review WHERE task.rev_id
=review.rev_id)
and task.rev_id=142) r;
Note : Here I tried static Rev_ID =142 to check data.
From above query i am getting output only if data exist in all four table, But if Data does not exist in any table, It does not return remaining value.
I want at-least names of all table's in final output.
Try the following, let us know if this meets your requirements.
SELECT rv.rev_id,
rv.rev_name,
mt.meeting_name,
tk.task_name,
ans.ans_name
FROM review rv
LEFT OUTER JOIN meeting mt ON (rv.rev_id = mt.rev_id)
LEFT OUTER JOIN task tk ON (rv.rev_id = tk.rev_id)
LEFT OUTER JOIN answer ans ON (rv.rev_id = ans.rev_id)
WHERE rv.rev_id = 142
SQL Fiddle Demo
If the above SQL is fine, prefix it with create table or view syntax to combine them into one.
I have two tables, with about 20 columns each
users:
id_user user ..... status token
----------------------------------
2 A 0 XdAQ
posts:
id_user post ..... status token
-------------------------------------
3 hi 1 sDyTMl
Query:
SELECT u.*,p.*
FROM posts as p
LEFT JOIN users as u ON u.id_user = p.id_user
WHERE p.id_post = 3
LIMIT 1
So in Php, it could be retrieved any value
....
$status=$a['status'];
$token=$a['token'];
I want to return all the fields of each table to make the post content, the problem is that there is conflict among those identical column names in each table. there are more than 20 columns in each in my real tables, so writing the column names with aliases I think is not the way to go. Is there a way to alias only those identical columns in conflict?
You really should list the specific columns that you want. This is the safest way to retrieve values from the table.
If the only column that is in common is the one used for the join, you can use the USING clause:
SELECT *
FROM posts p LEFT JOIN
users as u
USING (id_user)
WHERE p.id_post = 3
LIMIT 1;
The USING clause is ANSI standard, but not all databases support it. When you use it, only one version of id_post is in the columns returned by the SELECT *. In a LEFT JOIN, it is the version with a value.
If you have other columns with the same name, you need to use column aliases. One short-cut is to take all columns from one table and name the columns in the other:
SELECT u.*, p.col1 as p_col1, . . .
FROM posts p LEFT JOIN
users as u
USING (id_user)
WHERE p.id_post = 3
LIMIT 1;
I have been using SQL for years, but have mostly been using the query designer within SQL Studio (etc.) to put together my queries. I've recently found some time to actually "learn" what everything is doing and have set myself the following fairly simple tasks. Before I begin, I'd like to ask the SOF community their thoughts on the questions, possible answers and any tips they may have.
The questions are;
Find all records w/ a duplicate in a particular column (e.g. a linking id is in more than 1 record throughout table)
SUM price from a linked table within the same query (select within a select?)
Explain the difference between the 4 joins; LEFT, RIGHT, OUTER, INNER
Copy data from one table to another based on SELECT and WHERE criteria
Input welcomed & appreciated.
Chris
I recommend that you start by following some tutorials on this topic. Your questions are not uncommon questions for someone moving from a beginner to intermediate level in SQL. SQLZoo is an excellent resource for learning SQL so consider following that.
In response to your questions:
1) Find all records with a duplicate in a particular column
There are two steps here: find duplicate records and select those records. To find the duplicate records you should be doing something along the lines of:
select possible_duplicate_field, count(*)
from table
group by possible_duplicate_field
having count(*) > 1
What we're doing here is selecting everything from a table, then grouping it by the field we want to check for duplicates. The count function then gives me a count of the number of items within that group. The HAVING clause indicates that we want to filter AFTER the grouping to only show the groups which have more than one entry.
This is all fine in itself but it doesn't give you the actual records that have those values on them. If you knew the duplicate values then you'd write this:
select * from table where possible_duplicate_field = 'known_duplicate_value'
We can use the SELECT within a select to get a list of the matches:
select *
from table
where possible_duplicate_field in (
select possible_duplicate_field
from table
group by possible_duplicate_field
having count(*) > 1
)
2) SUM price from a linked table within the same query
This is a simple JOIN between two tables with a SUM of the two:
select sum(tableA.X + tableB.Y)
from tableA
join tableB on tableA.keyA = tableB.keyB
What you're doing here is joining two tables together where those two tables are linked by a key field. In this case, this is a natural join which operates as you would expect (i.e. get me everything from the left table which has a matching record in the right table).
3) Explain the difference between the 4 joins; LEFT, RIGHT, OUTER, INNER
Consider two tables A and B. The concept of "LEFT" and "RIGHT" in this case are slightly clearer if you read your SQL from left to right. So, when I say:
select x from A join B ...
The left table is "A" and the right table is "B". Now, when you explicitly say "LEFT" the SQL statement you are declaring which of the two tables you are joining is the primary table. What I mean by this is: Which table do I scan through first? Incidentally, if you omit the LEFT or RIGHT, then SQL implicitly uses LEFT.
For INNER and OUTER you are declaring what to do when matches don't exist in one of the tables. INNER declares that you want everything in the primary table (as declared using LEFT or RIGHT) where there is a matching record in the secondary table. Hence, if the primary table contains keys "X", "Y" and "Z", and the secondary table contains keys "X" and "Z", then an INNER will only return "X" and "Z" records from the two tables.
When OUTER is used, we're saying: Give me everything from the primary table and anything that matches from the secondary table. Hence, in the previous example, we'd get "X", "Y" and "Z" records in the output record set. However, there would be NULLs in the fields which should have come from the secondary table for key value "Y" as it doesn't exist in the secondary table.
4) Copy data from one table to another based on SELECT and WHERE criteria
This is pretty trivial and I'm surprised you've never encountered it. It's a simple nested SELECT in an INSERT statement (this may not be supported by your database - if not, try the next option):
insert into new_table select * from old_table where x = y
This assumes the tables have the same structure. If you have different structures then you'll need to specify the columns:
insert into new_table (list, of, fields)
select list, of, fields from old_table where x = y
Let's say you have 2 tables named :
[OrderLine] with the columns [Id, OrderId, ProductId, Qty, Status]
[Product] with [Id, Name, Price]
1) all orderline of command having more than 1 line (it's technically the same as looking for duplicates on OrderId :) :
select OrderId, count(*)
from OrderLine
group by OrderId
having count(*) > 1
2) total price for all order line of the order 1000
select sum(p.Price * ol.Qty) as Price
from OrderLine ol
inner join Product p on ol.ProductId = p.Id
where ol.OrderId = 1000
3) difference between joins:
a inner join b => take all a that has a match with b. if b is not found, a will be not be returned
a left join b => take all a, match them with b, include a even if b is not found
a righ join b => b left join a
a outer join b => (a left join b) union ( a right join b)
4) copy order lines to a history table :
insert into OrderLinesHistory
(CopiedOn, OrderLineId, OrderId, ProductId, Qty)
select
getDate(), Id, OrderId, ProductId, Qty
from
OrderLine
where
status = 'Closed'
To answer #4 and to perhaps show at least some understanding of SQL and the fact this isn't HW, just me trying to learn best practise;
SET NOCOUNT ON;
DECLARE #rc int
if #what = 1
BEGIN
select id from color_mapper where product = #productid and color = #colorid;
select #rc = ##rowcount
if #rc = 0
BEGIN
exec doSavingSPROC #colorid, #productid;
END
END
END