Hey i have a requirement to compare two tables of same structure.
Table1
EmpNO - Pkey
EmpName
DeptName
FatherName
IssueDate
ValidDate
I need to pass the EMPNO as parameter and I need to compare whether any of the column get changes? and return YES OR NO value.
can I able to do that using a PL/SQL Funcation? I was thinking of using the CONCAT in-build function to do that.
I'm trying the below one
Table1Concat = Select CONCAT(Column1.....6) from tbale1 where emp_no= in_empno;
Table2Concat = Select CONCAT(Column1.....6) from tbale2 where emp_no= in_empno;
IF(Table1Concat<>Table2Concat ) THEN return data_changed :='YES';
else data_changed :='NO';
END;
If you only want to detect whether any value is different then ...
select count(*)
from (select * from table1 where emp_no = my_emp_no
union
select * from table2 where emp_no = my_emp_no
)
If it returns 1 then the rows are the same, if it returns 2 then there is a difference.
The columns must be in the same order for this to work, or you'll have to list out all the column names in the order in which they match.
If you wanted to do this in bulk for a great many rows then you'd most likely use a different solution, s do not loop through every emp_no running this code for each one.
For bulk data where all emp_id's are present in both tables, use a query of the form:
select table1.emp_no,
case when table1.column1 = table2.column1 and
table2.column2 = table2.column2 and
table2.column3 = table2.column3 and
...
then 'Yes'
else 'No
end columns_match
from table1
join table2 on table1.emp_no = table2.emp_no
You can insert this result directly into a logging table.
Take care of null values though. "any_value = null" is never true, and "any_value != Null" is also never true, so you might need to add logic to take care of cases where one or both values are null.
Related
I need to render a query such that every column contains the count of a respective table.
The code I have now is:
SELECT COUNT(table1.Id),
COUNT(table2.Id),
COUNT(table3.Id)
FROM table1,
table2,
table3
WHERE table1.done = 'No' OR
table2.done = 'No' OR
table3.done = 'No' OR
But I need the query to return the same result values as if every table would be counted independently, like:
SELECT COUNT(tableX.Id) FROM tableX WHERE talbeX.done = 'No'
where the 'X' stands for 1,2 or 3.
How can this be achived with SQL?
Thanks beforhand for the help.
Just use a nested sub query, exactly as you have explained it:
SELECT
(SELECT COUNT(table1.Id) FROM table1 WHERE table1.done = 'No') as T1Count,
(SELECT COUNT(table2.Id) FROM table2 WHERE table2.done = 'No') as T2Count,
(SELECT COUNT(table3.Id) FROM table3 WHERE table3.done = 'No') as T3Count,
(SELECT COUNT(tableN.Id) FROM tableN) as TNCount;
This will query the tables independently so you are free to use what ever additional criteria you may need without trying to correlate the results from each query
FROM in this case is not strictly necessary in the outer query as we are not returning rows from any specific table, there is no table that we could specify in the from clause. Each RDBMS has their own convention for these types of queries, MS SQL Server and Oracle are to predominant database engines used in Outsystems
If we did specify a table in FROM then this would return 1 row for every record in that table, which is inefficient and not required. So it is important that we do not include a FROM clause.
Transact-SQL - FROM
The FROM clause is usually required on the SELECT statement. The exception is when no table columns are listed, and the only items listed are literals or variables or arithmetic expressions.
ORACLE - DUAL Table
DUAL is a table automatically created by Oracle Database along with the data dictionary. DUAL is in the schema of the user SYS but is accessible by the name DUAL to all users. It has one column, DUMMY, defined to be VARCHAR2(1), and contains one row with a value X. Selecting from the DUAL table is useful for computing a constant expression with the SELECT statement. Because DUAL has only one row, the constant is returned only once. Alternatively, you can select a constant, pseudocolumn, or expression from any table, but the value will be returned as many times as there are rows in the table.
Update - OP is using Oracle!
After attempting the solution, OP responded that it raised the following error:
Error in advanced query SQL2: ORA-00923: FROM keyword not found where expected
The ORA prefix of this error number indicates that the data store is actually an Oracle implementation, so we need to append the FROM DUAL to the query.
SELECT
(SELECT COUNT(table1.Id) FROM table1 WHERE table1.done = 'No') as T1Count,
(SELECT COUNT(table2.Id) FROM table2 WHERE table2.done = 'No') as T2Count,
(SELECT COUNT(table3.Id) FROM table3 WHERE table3.done = 'No') as T3Count,
(SELECT COUNT(tableN.Id) FROM tableN) as TNCount
FROM DUAL;
I am just learning SQL, and I'm wondering what the difference is between the following lines:
WHERE s.parent IN (SELECT l.parent .....)
versus
WHERE s.parent = (SELECT l.parent .....)
IN
will not generate an error if you have multiple results on the subquery. Allows to have more than one value in the result returned by the subquery.
=
will generate an error if you have more than one result on the subquery.
SQLFiddle Demo (IN vs =)
when you are using 'IN' it can compare multiple values....like
select * from tablename where student_name in('mari','sruthi','takudu')
but when you are using '=' you can't compare multiple values
select * from tablenamewhere student_name = 'sruthi'
i hope this is the right answer
The "IN" clause is also much much much much slower. If you have many results in the select portion of
IN (SELECT l.parent .....),
it will be extremely inefficient as it actually generates a separate select sql statement for each and every result within the select statement ... so if you return 'Cat', 'Dog', 'Cow'
it will essentially create a sql statement for each result... if you have 200 results... you get the full sql statement 200 times...takes forever... (This was as of a few years ago... maybe imporved by now... but it was horribly slow on big result sets.)
Much more efficient to do an inner join such as:
Select id, parent
from table1 as T
inner join (Select parent from table2) as T2 on T.parent = T2.parent
For future visitors.
Basically in case of equals (just remember that here we are talking like where a.name = b.name), each cell value from table 1 will be compared one by one to each cell value of all the rows from table 2, if it matches then that row will be selected (here that row will be selected means that row from table 1 and table 2) for the overall result set otherwise will not be selected.
Now, in case of IN, complete result set on the right side of the IN will be used for comparison, so its like each value from table 1 will be checked on whether this cell value is present in the complete result set of the IN, if it is present then that value will be shown for all the rows of the IN’s result set, so let say IN result set has 20 rows, so that cell value from table 1 will be present in overall result set 20 times (i.e. that particular cell value will have 20 rows).
For more clarity see below screen shot, notice below that how complete result set from the right of the IN (and NOT IN) is considered in the overall result set; whole emphasis is on the fact that in case comparison using =, matching row from second table is selected, while in case of IN complete result from the second table is selected.
In can match a value with more than one values, in other words it checks if a value is in the list of values so for e.g.
x in ('a', 'b', 'x') will return true result as x is in the the list of values
while = expects only one value, its as simple as
x = y returns false
and
x = x returns true
The general rule of thumb is:
The = expects a single value to compare with. Like this:
WHERE s.parent = 'father_name'
IN is extremely useful in scenarios where = cannot work i.e. scenarios where you need the comparison with multiple values.
WHERE s.parent IN ('father_name', 'mother_name', 'brother_name', 'sister_name')
Hope this is useful!!!
IN
This helps when a subquery returns more than one result.
=
This operator cannot handle more than one result.
Like in this example:
SQL>
Select LOC from dept where DEPTNO = (select DEPTNO from emp where
JOB='MANAGER');
Gives ERROR ORA-01427: single-row subquery returns more than one row
Instead use
SQL>
Select LOC from dept where DEPTNO in (select DEPTNO from emp
where JOB='MANAGER');
1) Sometimes = also used as comparison operator in case of joins which IN doesn't.
2) You can pass multiple values in the IN block which you can't do with =. For example,
SELECT * FROM [Products] where ProductID IN((select max(ProductID) from Products),
(select min(ProductID) from Products))
would work and provide you expected number of rows.However,
SELECT * FROM [Products] where ProductID = (select max(ProductID) from Products)
and ProductID =(select min(ProductID) from Products)
will provide you 'no result'. That means, in case subquery supposed to return multiple number of rows , in that case '=' isn't useful.
I've got a database like this one:
I'm trying to create a query that would enable me to update the value of the status attribute inside the incident table whenever the values of all of these three attributes: tabor_vatrogasci, tabor_policija, and tabor_hitna are contained inside the izvještaj_tabora table as a value of the oznaka_tabora attribute. If, for example, the values of the tabor_vatrogasci, tabor_policija, and tabor_hitna attributes are 3, 4 and 5 respectively, the incident table should be updated if (and only if) 3, 4, and 5 are contained inside the izvještaj_tabora table.
This is what I tried, but it didn't work:
UPDATE incident SET status='Otvoren' FROM tabor,izvjestaj_tabora
WHERE (incident.tabor_policija=tabor.oznaka
OR incident.tabor_vatrogasci=tabor.oznaka
OR incident.tabor_hitna=tabor.oznaka)
AND izvjestaj_tabora.oznaka_tabora=tabor.oznaka
AND rezultat_izvjestaja='Riješen' AND
((SELECT EXISTS(SELECT DISTINCT oznaka_tabora FROM izvjestaj_tabora)
WHERE oznaka_tabora=incident.tabor_policija) OR tabor_policija=NULL) AND
((SELECT EXISTS(SELECT DISTINCT oznaka_tabora FROM izvjestaj_tabora)
WHERE oznaka_tabora=incident.tabor_vatrogasci) OR tabor_vatrogasci=NULL) AND
((SELECT EXISTS(SELECT DISTINCT oznaka_tabora FROM izvjestaj_tabora)
WHERE oznaka_tabora=incident.tabor_hitna) OR tabor_hitna=NULL);
Does anyone have any idea on how to accomplish this?
Asuming INCIDENT.OZNAKA is the key and you need all 3 to be ralated for the event to open (I am Slovenian that why I understand ;) )
UPDATE incident
SET status='Otvoren'
WHERE oznaka in (
SELECT DISTINCT i.oznaka
FROM incident i
INNER JOIN izvještaj_tabora t1 ON i.tabor_vatrogasci = t1.oznaka_tabora
INNER JOIN izvještaj_tabora t2 ON i.tabor_policija = t2.oznaka_tabora
INNER JOIN izvještaj_tabora t3 ON i.tabor_hitna = t3.oznaka_tabora
WHERE t1.rezultat_izvjestaja='Riješen' AND t2.rezultat_izvjestaja='Riješen' AND t3.rezultat_izvjestaja='Riješen'
)
According to your description the query should look something like this:
UPDATE incident i
SET status = 'Otvoren'
WHERE (tabor_policija IS NULL OR
EXISTS (
SELECT 1 FROM izvjestaj_tabora t
WHERE t.oznaka_tabora = i.tabor_policija
)
)
AND (tabor_vatrogasci IS NULL OR
EXISTS (
SELECT 1 FROM izvjestaj_tabora t
WHERE t.oznaka_tabora = i.tabor_vatrogasci
)
)
AND (tabor_hitna IS NULL OR
EXISTS (
SELECT 1 FROM izvjestaj_tabora t
WHERE t.oznaka_tabora = i.tabor_hitna
)
)
I wonder though, why the connecting table tabor is irrelevant to the operation.
Among other things you fell victim to two widespread misconceptions:
1)
tabor_policija=NULL
This expression aways results in NULL. Since NULL is considered "unknown", if you compare it to anything, the outcome is "unknown" as well. I quote the manual on Comparison Operators:
Do not write expression = NULL because NULL is not "equal to" NULL.
(The null value represents an unknown value, and it is not known
whether two unknown values are equal.)
2)
EXISTS(SELECT DISTINCT oznaka_tabora FROM ...)
In an EXISTS semi-join SELECT items are completely irrelevant. (I use SELECT 1 instead). As the term implies, only existence is checked. The expression returns TRUE or FALSE, SELECT items are ignored. It is particularly pointless to add a DISTINCT clause there.
I've been trying for a few hours (probably more than I needed to) to figure out the best way to write an update sql query that will dissallow duplicates on the column I am updating.
Meaning, if TableA.ColA already has a name 'TEST1', then when I'm changing another record, then I simply can't pick a value for ColA to be 'TEST1'.
It's pretty easy to simply just separate the query into a select, and use a server layer code that would allow conditional logic:
SELECT ID, NAME FROM TABLEA WHERE NAME = 'TEST1'
IF TableA.recordcount > 0 then
UPDATE SET NAME = 'TEST1' WHERE ID = 1234
END IF
But I'm more interested to see if these two queries can be combined into a single query.
I am using Oracle to figure things out, but I'd love to see a SQL Server query as well. I figured a MERGE statement can work, but for obvious reasons you can't have the clause:
..etc.. WHEN NOT MATCHED UPDATE SET ..etc.. WHERE ID = 1234
AND you can't update a column if it's mentioned in the join (oracle limitation but not limited to SQL Server)
ALSO, I know you can put a constraint on a column that prevents duplicate values, but I'd be interested to see if there is such a query that can do this without using constraint.
Here is an example start-up attempt on my end just to see what I can come up with (explanations on it failed is not necessary):
ERROR: ORA-01732: data manipulation operation not legal on this view
UPDATE (
SELECT d.NAME, ch.NAME FROM (
SELECT 'test1' AS NAME, '2722' AS ID
FROM DUAL
) d
LEFT JOIN TABLEA a
ON UPPER(a.name) = UPPER(d.name)
)
SET a.name = 'test2'
WHERE a.name is null and a.id = d.id
I have tried merge, but just gave up thinking it's not possible. I've also considered not exists (but I'd have to be careful since I might accidentally update every other record that doesn't match a criteria)
It should be straightforward:
update personnel
set personnel_number = 'xyz'
where person_id = 1001
and not exists (select * from personnel where personnel_number = 'xyz');
If I understand correctly, you want to conditionally update a field, assuming the value is not found. The following query does this. It should work in both SQL Server and Oracle:
update table1
set name = 'Test1'
where (select count(*) from table1 where name = 'Test1') > 0 and
id = 1234
I am attempting to use a case statement but keep getting errors. Here's the statement:
select TABLE1.acct,
CASE
WHEN TABLE1.acct_id in (select acct_id
from TABLE2
group by acct_id
having count(*) = 1 ) THEN
(select name
from TABLE3
where TABLE1.acct_id = TABLE3.acct_id)
ELSE 'All Others'
END as Name
from TABLE1
When I replace the TABLE1.acct_id in the THEN expression with a literal value, the query works. When I try to use TABLE1.acct_id from the WHEN part of the query, I get a error saying the result is more than one row. It seems like the THEN expression is ignoring the single value that the WHEN statement was using. No idea, maybe this isn't even a valid use of the CASE statement.
I am trying to see names for accounts that have one entry in TABLE2.
Any ideas would be appreciated, I'm kind of new at SQL.
First, you are missing a comma after TABLE1.acct. Second, you have aliased TABLE1 as acct, so you should use that.
Select acct.acct
, Case
When acct.acct_id in ( Select acct_id
From TABLE2
Group By acct_id
Having Count(*) = 1 )
Then ( Select name
From TABLE3
Where acct.acct_id = TABLE3.acct_id
Fetch First 1 Rows Only)
Else 'All Others'
End as Name
From TABLE1 As acct
As others have said, you should adjust your THEN clause to ensure that only one value is returned. You can do that by add Fetch First 1 Rows Only to your subquery.
Then ( Select name
From TABLE3
Where acct.acct_id = TABLE3.acct_id
Fetch First 1 Rows Only)
Fetch is not accepting in CASE statement - "Keyword FETCH not expected. Valid tokens: ) UNION EXCEPT. "
select name from TABLE3 where TABLE1.acct_id = TABLE3.acct_id
will give you all the names in Table3, which have a accompanying row in Table 1. The row selected from Table2 in the previous line doesn't enter into it.
Must be getting more than one value.
You can replace the body with...
(select count(name) from TABLE3 where TABLE1.acct_id = TABLE3.acct_id)
... to narrow down which rows are returning multiples.
It may be the case that you just need a DISTINCT or a TOP 1 to reduce your result set.
Good luck!
I think that what is happening here is that your case must return a single value because it will be the value for the "name" column. The subquery (select acct_id from TABLE2 group by acct_id having count(*) = 1 ) is OK because it will only ever return one value. (select name from TABLE3 where TABLE1.acct_id= TABLE3.acct_id) could return multiple values depending on your data. The problem is you trying to shove multiple values into a single field for a single row.
The next thing to do would be to find out what data causes multiple rows to be returned by (select name from TABLE3 where TABLE1.acct_id= TABLE3.acct_id), and see if you can further limit this query to only return one row. If need be, you could even try something like ...AND ROWNUM = 1 (for Oracle - other DBs have similar ways of limiting rows returned).