I read up on SQL Join but as far as I understand it, you can only join tables which have a column name in common.
I have information in two different tables, but the column name is different in each. I need to pull information on something which is only in one of the tables, but also need information from the other. So was looking to join/merge them.
Here is what I mean..
TABLE1:
http://postimg.org/image/hnd63c2f5/
The cell content 18599 in column from_pin_id also pertains to content in another table:
TABLE2:
http://postimg.org/image/apmu26l5z/
My question is how do I merge the two table details so that it recognizes 18599 is referring to the same thing, so that I can pull content on it from other columns in TABLE2?
I've looked through the codes on W3 but cannot find anything to what I need, as mentioned above, it seems to be just for joining tables with a common column:
SELECT column_name(s)
FROM table1
JOIN table2
ON table1.column_name=table2.column_name;
You can write as :
select * from table1
where from_pin_id in
(
select from_pin_id
from table1
intersect
select id
from table2
)
Intersect operator selects all elements that belong to both of the sets.
Change the table names and the columns that you select as needed.
SELECT table1.id, table1.owner_user_id, table1.from_pin_id, table2.board_id
FROM table1
JOIN table2 ON table1.from_pin_id = table2.id
GROUP BY id, owner_user_id, from_pin_id, board_id
Related
I know that joins work by combining two or more tables by their attributes, so if you have two tables that both have three columns and both have column INDEX, if you use table1 JOIN table2 you will get a new table with 5 columns, but what if you do not have a column that is shared by both table1 and table2? Can you still use JOIN or do you have to use TIMES?
Join is not a method for combining tables. It is a method to select records (and selected fields) from 2 or more tables where every table in the query must carry a field that can be matched to a field in another table in the query. The matched fields need not have the same name, but must carry the same type of data. Lacking this would be like trying to create meaning from joining a list of license plates of cars in NYC, with height data from lumberjacks in Washington state -- not meaningful.
Ex:)
Select h.name, h.home_address, h.home_phone, w.work_address,
w.department
from home h, work w
where h.employee_id = w.emp_id
As long as both columns: employee_id and emp_id carry the same information this query will work
In Microsoft Access, to get five rows from a three column table joined to a two column table, you'd use:
SELECT Table1.*, Table2.* FROM Table1 INNER JOIN Table2 ON Table1.Field1 = Table2.Field1;
You can query whatever you want, and join whatever you want, though.
If your one table is a list of people, and your other is a list of cars, and you want to see what people have names that are also models of cars, you can do:
SELECT Table1.Name, Table1.Age, Table2.Make, Table2.Year
FROM Table1 INNER JOIN Table2 ON Table1.Name = Table2.Model;
Only when Name is the same as Model will it show a record.
This is the same idea for joining tables in any relational DBMS I've used.
You are right you can join two tables even if they do not have shared column.
Join uses primary to prevent mistakes on inserting or deleting when user trying to insert record that does not has a parent one or some thing like this.
join methods has many types you can view them here:
http://dev.mysql.com/doc/refman/5.7/en/join.html
LEFT JOIN: select all records from first table, then selecting all records from second table that fulfilling the condition after ON clause.
you can't join the tables if they do not share a common column. If you can find a 3rd table that has common columns with table1 and table2 you can get them to join that way. so join table2 and tabl3 on a common column and than join table3 back to table1 on a common column.
I have created a temporary that has been populated correctly but now I want to search another table based on two fields that are contained within my temporary table. These fields are Forename and Surname. But I want to search for multiple student names and quantities and return specified data! I think the problem will be better explained in the images below:
My Temporary Table
The Table I would like to search (Table2)
Once I have searched each student name I want to be returned with the students Forename, Surname Address, Pin and Score!
Below shows how I have been trying to achieve this without any luck!
Select TempTable.Forname, TempTable.Surmname, Table2.Address, Table2.Pin
from TempTable
Where Exists ( Select * from Table2
where Table2.Forname=TempTable.Forname and
Table2.Surname=TempTable.Surname
)
But it is returning me no results and I don't know why!
If i understand correctly your question, the way to do it is just a simple join:
select TempTable.Forename, TempTable.Surname, Table2.Address, Table2.Pin
from TempTable
inner join Table2 on Table2.Forename = TempTable.Forename and Table2.Surname = TempTable.Surname
Though i recommend you to have a primary key on the "Persons" table (Table2) and use this primary key to reference the records on TepTable
The EXISTS is only used to "filter" result, it's columns aren't available outside the EXISTS.
You need a JOIN!
Select TempTable.Forname, TempTable.Surmname, Table2.Address, Table2.Pin
from TempTable JOIN Table2 ON Table2.Forname=TempTable.Forname and Table2.Surname=TempTable.Surname;
Assuming you really have called the columns "Forname" you just need a simple join. This does it explicitly to keep close to your original:
SELECT TempTable.Forname, TempTable.Surmname, Table2.Address, Table2.Pin
FROM TempTable tt, Table2 t2
WHERE tt.Forename = t2.Forename
AND tt.Surname = t2.Surname;
You could do the same with INNER JOIN.
This is all assuming that student names are unique.
I have two tables
Table 1 has five columns
EmployeeID,
EmployeeCarModelID,
EmployeeCarModelName,
SpouseCarModelID,
SpouseCarModelName
Table 2 has two columns
CarModelID,
CarModelName
How would I construct a select statement which will pull through the CarModelName to both the EmployeeCarModelName and the SpouseCarModelName based on their respective IDs? I'm not sure I can use a JOIN statement to do this as we are looking at two different id columns within the same table.
You need two joins to do this. I think you want:
select t1.EmployeeId, t1.EmployeeCarModelID, t2emp.CarModelName as EmployeeCarModelName,
t1.SpouseCarModelID, t2sp.CarModelName as SpouseCarModelName
from table1 t1 left join
table2 t2emp
on t1.EmployeeCarModelID = t2emp.CarModelId left join
table2 t2sp
on t1.SpouseCarModelId = t2sp.CarModelId;
Say I've got a query like this:
select table1.id, table1.name
from table1
inner join table2 on table1.id = table2.id
where table1.name = "parent" and table2.status = 1
Is it true that, since there's an inner join, I can refer the table2's status column even from table1? Like this:
select table1.id, table1.name
from table1
inner join table2 on table1.id = table2.id
where table1.name = "parent" and table1.status = 1
And if yes, what's the best of the two ways?
If I am not mistaken, you are asking that in an inner join, two fields of the same name, data type and length will be one field in the particular query. Technically that is not the case. Regardless of anything, Table1.Status will refer to Table1 and Table2.Status will refer to Table2's condition/value.
The two queries above CAN product different results from each other.
A good rule on this is that you stick your conditions on the base table, or Table1, in this case. If a field is exclusive to another table, that's when you'll use that Table's field.
No, that's not true. By Inner join what you are doing is say if you have table1 with m rows and table two with n rows then the third SET that will be produced by joining the two tables will have m*n rows based on match condition that you have mentioned in where clause. It's not m+n rows or infact columns of the two tables are not getting merged at database level. status column will remain in the table it has been defined.
Hope that helps!!!
You can see this is not the case if you do
CREATE TABLE table1 (id INT, name VARCHAR);
CREATE TABLE table2 (id INT, status INT);
Now if you run your second query you will get an error because you refer to t1.status, and the status column does not existing in table t1.
If there was a status field in both tables the query would run, but likely would not give the results you want e.g. assume status in table1 was always 1, and in table2 was always 0. Now your first query could never return rows, but your second one certainly could return rows.
I am trying to deduplicate a large table where values are present but broken into several rows.
For example:
Table 1: Client_Code,Account#, First and last names, address.
Table 2: Client_Code,Account#, First and last names, address, TAX_ID.
Now what I want to do may seem pretty obvious at this point.
I want my results to pull from Table 1 into a new table and the query to be "Select From Table 1 where client code and account# from table 1 match client code and account# from table 2." TAble 2 has all values populated, Table 1 has everyone except TAX ID.
The code i tried looked like this.
CREATE TABLE Dedupe_1 AS SELECT * FROM `TABLE 1`
WHERE `TABLE 1`.`Client_Code`=`TABLE 2`.`Client_Code`
AND
WHERE `TABLE 1`.`account#`=`TABLE 2`.`account#`
ORDER BY `TABLE 2`.`account#`
I keep getting a syntax error. I am very new to this programming language so I apologize if this question is hard to understand.
I was just under the impression that I could call to a field from another table by simply using the 'WHERE' statement.
I think you want to use an exists clause:
CREATE TABLE Dedupe_1 AS
SELECT *
FROM `TABLE 1` t1
WHERE EXISTS (select 1
from table2 t2
where t2.Client_Code = t1.Client_Code and t2.`account#` = t1.`account#`
);
You may want to use Join to connect two tables. You can make use of common column among two tables for Join statement. Common syntax goes like
SELECT table1.column1, table2.column 2 and as many you want in common table
FROM table1 name
INNER JOIN table2 name
ON table1.commoncolumn=table2.Common column;
You may learn more about joins here.