OK so my question is: There a difference in record count depending on where the AND statement is positioned within my query. For instance, if I have several INNER JOINS and a couple LEFT Joins and at the very end of my query if I place all my AND statements the record count is different then if I place my AND statement right below the matching JOIN table. Since the AND statement specifies the table, why would it matter where its placed within the query?
Example 1:
FROM table (nolock)
INNER JOIN table2 (nolock) ON Table.ID = table2.ID
INNER JOIN table3 (nolock) ON table2.ID = table3.ID
LEFT JOIN table4 (nolock) ON table3.ID = table4.ID
where table.vendor = 1234
AND table.Active = 1
And table2.Active = 1
And table3.Active = 1
and table4.Active = 1
and table3.Name LIKE 'someName'
Example 2:
FROM table (nolock)
INNER JOIN table2 (nolock) ON Table.ID = table2.ID
And table2.Active = 1
INNER JOIN table3 (nolock) ON table2.ID = table3.ID
And table3.Active = 1
and table3.Name LIKE 'someName'
LEFT JOIN table4 (nolock) ON table3.ID = table4.ID
where table.vendor = 1234
and table4.Active = 1
AND table.Active = 1
When using INNER JOIN it makes no difference whether the criteria accompanies the JOIN or if it's in the WHERE clause, however with LEFT JOIN adding join criteria doesn't filter out non-joining records, but that criteria in the WHERE clause will exclude non-joining records. In your case WHERE table4.Active = 1 excludes non-joining records from table4, but moving that criteria to the JOIN will not exclude those records.
Here is a simple demonstration: SQL Fiddle
Note: I've made the assumption that your sample code isn't quite right and that this is the problem based on your description.
Related
I have three tables and I have to write one query to update table 1 row from table 3 and the only matching columns I have is in table 2.
Table 1 which has incorrect data:
Table 3 has the correct data:
I did try to write a query and execute it but it gives me an error saying there are too many rows too select which is true I do have many rows to correct but it still wouldn't correct. What do you think I should do. This is my query so far.
UPDATE Table1
SET Table1.Number = (SELECT Table3.Number
FROM Table2
FULL OUTER JOIN Table1 ON Table1.ID = Table2.ID
FULL OUTER JOIN Table3 ON Table3.Signin = Table2.Signin
WHERE (Table2.ID = Table1.ID)
AND (Table1.Number = 'xxx'))
WHERE (Tale1.Number = 'xxx')
In Where clause of JOIN query need to modify as multiple records are generating by inappropriate condition.Try to use Table3 components instead of using Table1 in joining query where clause.
UPDATE Table1
SET Table1.NUMBER = (SELECT table3.NUMBER FROM Table1 FULL OUTER JOIN Table2
ON Table1.ID = Table2.ID
FULL OUTER JOIN Table3
ON Table2.SIGNIN = Table3.SIGNIN
WHERE Table3.SIGNIN = 100) // This is the point where you need to modify your code
WHERE Table1.ID = 1;
ONLINE DEMO HERE
It actually worked after I removed this line from my query.
FULL OUTER JOIN Table1 ON table1.ID = Table2.ID
Thanks for the help.
You are fairly close. When doing the update though unless you are wanting to clear value for t1.number when a record is not matched in t3, you will want to use INNER JOIN. FULL OUTER JOIN would mean you are trying to update rows in t1 that don't exist but a LEFT JOIN you would update t1.number to NULL if a record in t3 doesn't exist.
UPDATE t1
SET t1.Number = t3.Number
FROM
Table1 t1
INNER JOIN Table2 t2
ON t1.Id = t2.Id
INNER JOIN Table3 t3
ON t2.Signin = t.3.Signin
WHERE
t1.number <> t3.number
--Or if you have nulls something like
--ISNULL(t1.number,'xxx') <> ISNULL(t3.number,'xxx')
-- if you only want to update when t1.number = 'xxx' then
--t1.number = 'xxx'
t1,t2,t3 are table aliases that I created by adding the alias after table name. By using join syntax rather than a sub select you simplify your were conditions. In sql-sever if more than 1 record in t2 & t3 match it will select one row randomly in the case of a one to many relationship. If you want a specific record when not one to one relation you can use window functions and common table expressions (cte) to limit t3 to the exact record you want to use.
I've to make a query on Oracle and i'm a little bit stuck with it. In my TABLE1, I've 287 reccords so I want all informations from TABLE2 AND TABLE3 that egal with my 287 reccords (that's why I use Left Join). But I also want all reccords that match between TABLE2 and TABLE4, TABLE4 AND TABLE5 (That's why I use Inner Join).
But my query don't work and I don't know why. Someone can help me ?
My query :
SELECT distinct(TABLE1.NUM_SIN),
TABLE1.LIBELLE,
TABLE1.DATE_FRAIS,
TABLE2.CODE_SIN,
TABLE2.PKPR,
TABLE1.MT,
TABLE4.POSTBUD,
TABLE3.VEENG
FROM TABLE1
LEFT JOIN TABLE2
ON TABLE2.NUM_SIN = TABLE1 .NUM_SIN
INNER JOIN TABLE4
ON TABLE4.NUM_SIN = TABLE2.NUM_SIN
AND TABLE4.SCSO = TABLE2.SCSO
LEFT JOIN TABLE5
ON TABLE5.CDC = TABLE4.NO
AND TABLE5.CDEXE = TABLE4.CDEXE
AND TABLE5.SCSO = TABLE4.SCSO
LEFT JOIN TABLE3
ON TABLE3.CNCT = TABLE1.NUM_SIN
WHERE ... ;
A graph to understand :
Thx in advice !
I think the issue here is perhaps that you really don't want to use an inner join in your query, and perhaps that you don't know exactly what the difference is between an inner join and an outer join.
The inner join in your query will return ONLY the rows from TABLE4 that are a match in TABLE2. Joins are sequential and cumulative, so your remaining LEFT joins will have the reduced rowset on the left side of the join.
Thus, I believe you will want to use LEFT joins throughout your query, e.g.:
SELECT distinct(TABLE1.NUM_SIN),
TABLE1.LIBELLE,
TABLE1.DATE_FRAIS,
TABLE2.CODE_SIN,
TABLE2.PKPR,
TABLE1.MT,
TABLE4.POSTBUD,
TABLE3.VEENG
FROM TABLE1
LEFT JOIN TABLE2
ON TABLE2.NUM_SIN = TABLE1 .NUM_SIN
LEFT JOIN TABLE4
ON TABLE4.NUM_SIN = TABLE2.NUM_SIN
AND TABLE4.SCSO = TABLE2.SCSO
LEFT JOIN TABLE5
ON TABLE5.CDC = TABLE4.NO
AND TABLE5.CDEXE = TABLE4.CDEXE
AND TABLE5.SCSO = TABLE4.SCSO
LEFT JOIN TABLE3
ON TABLE3.CNCT = TABLE1.NUM_SIN
WHERE ... ;
Are you sure you don't want to left join to table4? The way it is written only values in TABLE4 would be allowed which would limit the results from table2 and table5.
NB - the image CDN is filtered here so I can't see the image.
SELECT --
FROM TABLE1
LEFT JOIN TABLE2 ON TABLE2.NUM_SIN = TABLE1 .NUM_SIN
LEFT JOIN TABLE3 ON TABLE3.CNCT = TABLE1.NUM_SIN
-- unless you want to reduce the number of table2 rows use left join here.
LEFT JOIN TABLE4 ON TABLE4.NUM_SIN = TABLE2.NUM_SIN AND TABLE4.SCSO = TABLE2.SCSO
LEFT JOIN TABLE5 ON TABLE5.CDC = TABLE4.NO
AND TABLE5.CDEXE = TABLE4.CDEXE
AND TABLE5.SCSO = TABLE4.SCSO
WHERE ... ;
I have 3 models. Table1 belongs to Table2, and Table2 belongs to Table3.
I want to get an ActiveRecord::Relation that includes all of the fields from all 3 tables, including nulls (outer joining to get all of Table1), with a WHERE clause on Table1 and an order by a column in Table3.
What I want in SQL is:
SELECT * FROM Table1 LEFT OUTER JOIN Table2 ON Table2.id = Table1.table2_id
LEFT OUTER JOIN Table3 ON Table3.id = Table2.table3_id
WHERE Table1.column1 = "example"
ORDER BY Table3.table3_column
However, I have been trying for hours now to do this in rails and getting nowhere. Is it possible?
#records = Table1.joins(:table2).joins(:table3).where(:column1 => "example").order("table3_column")
(For example), gets me nowhere because it is looking for an association between Table1 and Table3, which doesn't exist other than through Table2. I need to join once, then join on top of that. Not to mention that is an inner join. I've tried of the form:
#records = Table1.joins("LEFT OUTER JOIN Table2 ON Table2.id = Table1.table2_id LEFT OUTER JOIN Table3 ON Table3.id = Table2.table3_id")
But I get nil from that.
Thanks for any help with this.
Try find_by_sql
Table1.find_by_sql("SELECT * FROM Table1
LEFT OUTER JOIN Table2 ON Table2.id = Table1.table2_id
LEFT OUTER JOIN Table3 ON Table3.id = Table2.table3_id
WHERE Table1.column1 = "example"
ORDER BY Table3.table3_column")
refer find by sql
How do I write an Oracle query which is equivalent to the following Informix query?
select tab1.a,tab2.b,tab3.c,tab4.d
from table1 tab1,
table2 tab2 OUTER (table3 tab3,table4 tab4,table5 tab5)
where tab3.xya = tab4.xya
AND tab4.ss = tab1.ss
AND tab3.dd = tab5.dd
AND tab1.fg = tab2.fg
AND tab4.kk = tab5.kk
AND tab3.desc = "XYZ"
I tried:
select tab1.a,tab2.b,tab3.c,tab4.d
from table1 tab1,
table2 tab2 LEFT OUTER JOIN (table3 tab3,table4 tab4,table5 tab5)
where tab3.xya = tab4.xya
AND tab4.ss = tab1.ss
AND tab3.dd = tab5.dd
AND tab1.fg = tab2.fg
AND tab4.kk = tab5.kk
AND tab3.desc = "XYZ"
What is the correct syntax?
Write one table per join, like this:
select tab1.a,tab2.b,tab3.c,tab4.d
from
table1 tab1
inner join table2 tab2 on tab2.fg = tab1.fg
left join table3 tab3 on tab3.xxx = tab1.xxx and tab3.desc = "XYZ"
left join table4 tab4 on tab4.xya = tab3.xya and tab4.ss = tab3.ss
left join table5 tab5 on tab5.dd = tab3.dd and tab5.kk = tab4.kk
Note that while my query contains actual left join, your query apparently doesn't.
Since the conditions are in the where, your query should behave like inner joins. (Although I admit I don't know Informix, so maybe I'm wrong there).
The specfific Informix extension used in the question works a bit differently with regards to left joins. Apart from the exact syntax of the join itself, this is mainly in the fact that in Informix, you can specify a list of outer joined tables. These will be left outer joined, and the join conditions can be put in the where clause. Note that this is a specific extension to SQL. Informix also supports 'normal' left joins, but you can't combine the two in one query, it seems.
In Oracle this extension doesn't exist, and you can't put outer join conditions in the where clause, since the conditions will be executed regardless.
So look what happens when you move conditions to the where clause:
select tab1.a,tab2.b,tab3.c,tab4.d
from
table1 tab1
inner join table2 tab2 on tab2.fg = tab1.fg
left join table3 tab3 on tab3.xxx = tab1.xxx
left join table4 tab4 on tab4.xya = tab3.xya
left join table5 tab5 on tab5.dd = tab3.dd and tab5.kk = tab4.kk
where
tab3.desc = "XYZ" and
tab4.ss = tab3.ss
Now, only rows will be returned for which those two conditions are true. They cannot be true when no row is found, so if there is no matching row in table3 and/or table4, or if ss is null in either of the two, one of these conditions is going to return false, and no row is returned. This effectively changed your outer join to an inner join, and as such changes the behavior significantly.
PS: left join and left outer join are the same. It means that you optionally join the second table to the first (the left one). Rows are returned if there is only data in the 'left' part of the join. In Oracle you can also right [outer] join to make not the left, but the right table the leading table. And there is and even full [outer] join to return a row if there is data in either table.
I'm guessing that you want something like
SELECT tab1.a, tab2.b, tab3.c, tab4.d
FROM table1 tab1
JOIN table2 tab2 ON (tab1.fg = tab2.fg)
LEFT OUTER JOIN table4 tab4 ON (tab1.ss = tab4.ss)
LEFT OUTER JOIN table3 tab3 ON (tab4.xya = tab3.xya and tab3.desc = 'XYZ')
LEFT OUTER JOIN table5 tab5 on (tab4.kk = tab5.kk AND
tab3.dd = tab5.dd)
I'm trying to execute a query that looks similar to this:
SELECT <columns> FROM table1
INNER JOIN table2 ON table1.id = table2.table1_id
INNER JOIN table3 ON table1.id = table3.table1_id
WHERE table3.column1 != 'foo' AND <other_conditions>
LIMIT 1;
The thing is--I want the query to return a result regardless of whether the record in table3 exists or not. That is--if the record in table3 is present, I want to check whether that record has a certain column value. If the record in table3 doesn't exist, I want the query to assume that the condition is TRUE.
Any pointers?
You use a left join on the table. If no corresponding record exists, the value from the table will be null, so you can use coalesce to get a value that you can compare to the string:
SELECT <columns> FROM table1
INNER JOIN table2 ON table1.id = table2.table1_id
LEFT JOIN table3 ON table1.id = table3.table1_id
WHERE COALESCE(table3.column1, '') != 'foo' AND <other_conditions>
LIMIT 1
You've come to a point where you noticed that there is a difference between WHERE conditions and JOIN conditions.
SELECT
<columns>
FROM
table1
INNER JOIN table2 ON table2.table1_id = table1.id
LEFT JOIN table3 ON table3.table1_id = table1.id AND table3.column1 <> 'foo'
WHERE
<other_conditions>
LIMIT 1;
You need to use an outer join to include table3 instead of an inner join.