I used this code in SQL Server to join two tables on unique values i made with concat.
My intention was to create unique values with concat function in both tables so I can join them on matching values.
Problem is that query written in this way never never executes (like some sort of infinite loop)
[Table inputs and result]
select t1.AAA, t1.BBB, t1.XXX, t2.YYY
from Table1 t1
inner join Table2 t2
on concat(t1.AAA, t1.BBB)= CONCAT(t2.AAA, t2.BBB)
why concat , this way you lose benefit of optimizer & index ,
you can join on two condition :
select select t1.AAA, t1.BBB, t1.XXX, t2.YYY
from Table1 t1
inner join Table2 t2
on t1.AAA= t2.AAA
and t1.BBB = t2.BBB
The query that you want is:
select t1.AAA, t1.BBB, t1.XXX, t2.YYY
from Table1 t1 inner join
Table2 t2
on t1.AAA = t2.AAA and t1.BBB = t2.BBB;
Then, if performance is a concern, you want an index on Table1(AAA, BBB) or Table2(AAA, BBB) or both. The columns can also be reversed in the indexes.
Related
I want to join two tables in Access based on different wildcards for different rows.
The first, table1, contains rows with different wildcards and table2 contains the column that should be matched with the wildcards in table1.
I imagine the SQL code to look like:
SELECT *
FROM table2
LEFT JOIN table1
ON table2.subject LIKE table1.wildcard
The tables look like this: https://imgur.com/a/O9OPAL6
The third pictures shows the result that I want.
How do I execute the join or is there an alternative?
I don't think MySQL support non-equality conditions for JOINs. So, you can do this as:
SELECT * -- first get the matches
FROM table2 as t2, -- ugg, why doesn't it support CROSS JOIN
table1 as t1
WHERE t2.subject LIKE t1.wildcard
UNION ALL
SELECT * -- then get the non-matches
FROM table2 as t2 LEFT JOIN
table1 as t1
ON 1 = 0 -- always false but gets the same columns
WHERE NOT EXISTS (SELECT 1
FROM table1 as t1
WHERE t2.subject LIKE t1.wildcard
);
I need to merge below Table 1 & Table 2 as indicated in "Merge".
The query I wrote below works; but it is TOO SLOW! Is there any simpler way which returns it faster?
SELECT T1.Loc, T2.SO, T2.PO, T1.Item
FROM Table1 T1
LEFT OUTER JOIN Table2 T2
ON ISNULL(T1.[SO2],T1.[SO1]) = T2.[SO]
Never use commas in the FROM clause. Always use proper, explicit JOIN syntax:
SELECT *
FROM Table1 T1 LEFT OUTER JOIN
Table2 T2
ON COALESCE(T1.[SO2], T1.[SO1]) = T2.[SO];
There is no need to join to Table2 twice (much less getting a Cartesian product). I prefer COALESCE() to ISNULL() simply because the former is the ANSI standard function for replacing NULL values.
I should add that for performance, two joins might be preferable:
SELECT T1.Loc, COALESCE(T2_2.SO, T2_1.SO) as SO,
COALESCE(T2_2.PO, T2_1.PO) as PO, T1.Item
FROM Table1 T1 LEFT OUTER JOIN
Table2 T2_2
ON T1.[SO2] = T2_2.[SO] LEFT OUTER JOIN
Table2 T2_1
ON T1.[SO1] = T2_1.[SO] AND T1.[SO2] IS NULL;
It is easier for the SQL engine to optimize joins that use only equality and AND conditions, on the clean column references (that is, the columns are not the arguments to any function calls).
Hope this SQL full fill your requirement.
Select T2.Loc, T2.SO, T2.PO, T1.item from table 2 T2 join table1 T1
on T1.SO1 = T2.SO;
I am trying to write an SQL query that will return Table1, which has 10 columns. This table consists of a primary key id, 4 foreign key Id columns, and 5 other columns that I want to return but not change. The goal is to do a join to replace the foreign key Ids with their descriptions that are held in other tables.
Here is one attempt with the first FK Id:
Select * from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
This left join returns the description from table2, but does not replace it.
Here is another with the first FK Id:
Select t2.BranchName from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
This returns the name I want, but does not return table1 fully.
For the sake of an example you could pretend that OtherName3, OtherName4, OtherName5 are in tables Table3, Table4, Table5, respectively.
This may seem trivial for experienced SQL devs, but I am having a hard time figuring out the syntax.
Thanks!
I'm not sure what you mean by replace it.
I think you just need to list out all the columns you want:
Select t1.col1, t1.col2, t1.col3, . . .,
t2.name
from Table1 t1 left join
Table2 t2
on t1.BranchId = t2.BranchId;
I don't know what you mean by 'replace' but you just need to qualify what columns from which table you want. That goes for all tables you are joined to, especially if they have the same column name in multiple tables. I put junk columns in since I don't know your tables but you should get the general idea.
Select t2.BranchName, t1.BranchId, t1.Name, t1.Amount, t2.BranchLocation from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
I think this is what you are looking for:
select t1.*, t2.BranchName from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
Return Table1 fully (all columns) and only the description (BranchName) from Table2.
If using SQL Server, see all syntax options for the SELECT clause here:
https://msdn.microsoft.com/en-us/library/ms176104.aspx
Suppose I have two tables T1 & T2. I want resulting output table as O1 with help of a SQL query
T1 {SName}
T2 {VName}
O1 {SName, VName}
It seems like you want a cross join of the two tables to include all combinations of rows in T1 and T2. Try this:
Select SName, VName From T1 Inner Join T2 On 1=1
The number of rows you will get is the product of the number of rows in T1 and T2 each.
if you're not joining on anything and want a table of all possible combinations:
select SName, VName
into O1
from T1 cross join T2
if you have a column to join on:
select SName, VName
into O1
from T1 inner join T2 on T1.col = T2.col
Select record from T1 and T2 based on filtering criteria and then insert record in table O1 , use below query to create table O1 and inserting those records.
INSERT INTO O1(SNAME, VNAME)
SELECT(T1.SNAME, T2.VNAME)
From T1 Inner Join T2 On 1=1 //i.e WHERE T1.id=T2.T1_id
use WHERE to filter records
there are several ways of doing it.one easy way is:
select T1.SName,T2.VName from T1,T2;
i don't know if i am right, you can use cross join.
if you have two tables Players and GameScores then
SELECT* INTO O1 FROM GameScores CROSS JOIN Players will return all records where each row from the first table is combined with each row from the second table. Which also mean CROSS JOIN returns the Cartesian product of the sets of rows from the joined tables.
to get the above result as
T1 {SName}
T2 {VName}
O1 {SName, VName}
(SELECT * FROM T1,T2) as O1;
will definitely work if both the table have single value if not then you can select the
Particular column like T1.SName,T2.VName
I am a little confused as to how to approach this SQL query.
I have two tables (equal number of records), and I would like to return a column with which is the division between the two.
In other words, here is my not-working-correctly query:
SELECT( (SELECT v FROM Table1) / (SELECT DotProduct FROM Table2) );
How would I do this? All I want it a column where each row equals the same row in Table1 divided by the same row in Table2. The resulting table should have the same number of rows, but I am getting something with a lot more rows than the original two tables.
I am at a complete loss. Any advice?
It sounds like you have some kind of key between the two tables. You need an Inner Join:
select t1.v / t2.DotProduct
from Table1 as t1
inner join Table2 as t2
on t1.ForeignKey = t2.PrimaryKey
Should work. Just make sure you watch out for division by zero errors.
You didn't specify the full table structure so I will assume a common ID column to link rows in the tables.
SELECT table1.v/table2.DotProduct
FROM Table1 INNER JOIN Table2
ON (Table1.ID=Table2.ID)
You need to do a JOIN on the tables and divide the columns you want.
SELECT (Table1.v / Table2.DotProduct) FROM Table1 JOIN Table2 ON something
You need to substitue something to tell SQL how to match up the rows:
Something like: Table1.id = Table2.id
In case your fileds are both integers you need to do this to avoid integer math:
select t1.v / (t2.DotProduct*1.00)
from Table1 as t1
inner join Table2 as t2
on t1.ForeignKey = t2.PrimaryKey
If you have multiple values in table2 relating to values in table1 you need to specify which to use -here I chose the largest one.
select t1.v / (max(t2.DotProduct)*1.00)
from Table1 as t1
inner join Table2 as t2
on t1.ForeignKey = t2.PrimaryKey
Group By t1.v