I've been doing research and cannot find a way to get data from multiple tables using one query. What I want to achieve is getting information from one table in an Access database and using that information to get more data from a different table in the same database
Here's the code I have so far...
string end = "ENDDATE";
string qual = "CGA0113";
string start = "START";
ad.SelectCommand = new OleDbCommand("SELECT* FROM [AC_ECONOMIC] Where KEYWORD = '" + end + "'AND QUALIFIER = '" + qual + "' AND EXPRESSION LIKE 'SN%'", con);
I want to be able to get data from a separate table called AC_PROPERTY with the same SN from the query above from that AC_ECONOMIC table. I was researching joins and believe that is the way to go but I'm not quite sure of the syntax or if that would even work. Any help would be greatly appreciated.
Correct, an inner join would be the way to go. You basically need to construct a statement that joins the 2 tables by their common field. Something like this:
SELECT * FROM [AC_ECONOMIC] a
INNER JOIN [AC_PROPERTY] b
on [AC_ECONOMIC].SN=[AC_PROPERTY].SN
Where KEYWORD = '" + end + "'AND QUALIFIER = '" + qual + "' AND EXPRESSION LIKE 'SN%'
Above statement is just an example. I don't know if the common column between the 2 tables is actually called "SN".
UPDATE:
As suggested by #Geek, you can also alias the tables after you reference them in your statement, this saves you from typing the full table names every time. For example, the above statement can also be written as:
SELECT a.*, b.* FROM [AC_ECONOMIC] a
INNER JOIN [AC_PROPERTY] b
on a.SN=b.SN
Where a.KEYWORD = '" + end + "'AND a.QUALIFIER = '" + qual + "' AND b.EXPRESSION LIKE 'SN%'
Note how the WHERE clause is filtering using columns from both, "a" (AC_ECONOMIC) and b (AC_PROPERTY).
Related
Can you please show me where I can INNER JOIN the tables for the FK_roomTypesID, FK_BedTypeID and FK_roomViewsID? All of the FK are on different tables from the primary.
MySqlDataAdapter da = new MySqlDataAdapter("SELECT RoomNo, RoomBedsNo,
RoomSmoking, RoomMiniBar,RoomKitchen,RoomFirePlace,RoomBalcony, RoomVeranda,
RoomGarden, RoomEntrance, RoomAirCondition, RoomTV, FK_roomTypesID,
FK_BedTypeID, FK_roomViewsID FROM tblrooms WHERE roomsID NOT IN(SELECT FK_roomsID
FROM tblbooking WHERE '" + arrdate + "' < checkOutDate AND '" + depdate + "' >
checkInDate)", conn);
You have the following part in your query:
FROM tblrooms
You define your joins in your FROM clause, therefore you should modify the code above to something like:
FROM tblrooms
join tblroomtypes
on tblrooms.FK_roomTypesID = tblroomtypes.roomTypesID
join tblbedtypes
on tblrooms.FK_bedTypesID = tblbedtypes.bedTypesID
join tblroomviews
on tblrooms.FK_roomViewsID = tblroomviews.roomViewsID
Note, that you did not give too much information, so I am guessing your table and column names here. Also, note, that I did not select any new columns. Finally, note, that you need to resolve ambiguity if the problem is applicable to your case by referring to your columns as table's columns. And format your code, it is difficult to read it. I did not use the inner keyword for the joins, because join is inner by default.
I have three tables, one holds a list of available products with relevant details such as product price, the other holds orders and the last holds specific order details including the items purchased in an order.
I am trying to create a query to calculate the total price of an order by linking the two of the tables with an inner join and then updating the order table with the value. The code I have written contains syntax errors, being a novice I have probably made an obvious mistake but any help would be appreciated.
"SELECT Sum(ProductTable.prodPrice) AS Total, OrderDetailTable.orderID " +
"FROM ProductTable INNER JOIN OrderDetailTable " +
"ON ProductTable.prodID = OrderDetailTable.prodID " +
"GROUP BY OrderDetailTable.orderID " +
"HAVING OrderDetailTable.orderID = ? " +
"UPDATE OrderTable " +
"SET " +
"totalPrice = Total " +
"WHERE OrderTable.orderID = ? ";
I am using Access.
I also forgot to mention that the ? is represented using a Dataview parameter
pc.Add(new Parameter("?", TypeCode.Int32, basketId.ToString()));
EDIT: Using PaqoGomez's suggestion to declare Total as a value I now get the error : Syntax error (missing operator) in query expression '0WHERE OrderTable.orderID = ?'.
Comment made before OP described this as MS Access:
Haven't tried this but you had the Select and update the wrong way round. This should be quite close. Its been a while for me but you may need to change the FROM clause to reference the table you are updating and INNER JOIN the sub-select instead of the WHERE clause.
"UPDATE OrderTable " +
"SET totalPrice = Sum(ProductTable.prodPrice)" +
"FROM (" +
"SELECT OrderDetailTable.orderID, Sum(ProductTable.prodPrice)" +
"FROM ProductTable INNER JOIN OrderDetailTable " +
"ON ProductTable.prodID = OrderDetailTable.prodID " +
"GROUP BY OrderDetailTable.orderID " +
") x" +
"WHERE x.orderID = OrderTable.OrderId"
UPDATE :
Based on OPs update regarding MS Access you can do an update with a sub-query, but I think it depends on the version of MS Access you are using and how you do it. Posts below seem to indicate it's quite problematic:
SQL Subqueries (Microsoft Access SQL)
How do I perform update query with subquery in Access?
Can It Be Done - Access 2007 SQL Update Query Using a Subquery?
By declaring a variable you can save the total value so that you can use it in the later update.
declare #Total int;
SELECT #Total = Sum(ProductTable.prodPrice)
//...
"SET " +
"totalPrice = #Total "
You dont mention which database platform you are using, I'm assuming MSSQL, other platforms would require a slightly different syntax.
You might also be interested to know that if you use the # symbol you can have a multiline string. This would allow you to avoid the concatenation that you are doing. eg.
var sql = #"some
sql
string"
I have a GridView in my application, where I am supposed to show list of records by joining different tables. The SQL Join query shows records but say within 1000 rows it shows 2 to 3 records twice. Is it because of the sql query?
The SQL Query I am using is:
SqlDataAdapter da = new SqlDataAdapter("select dt.name, rg.sex, ad.dt_adm, st.* " +
"from stdn_st st, stdn_reg rg, stdn_det dt, admsn_det ad where st.college='" +
lbl_college.Text + "' and st.course='" + lbl_course.Text + "' and st.sem='" +
lbl_sem.Text + "' and st.pass='" + lbl_pass.Text + "' and rg.id=st.sid and " +
"dt.sid=st.sid and ad.sid=st.sid", con);
Use latest syntax of join. As per your requirement you can use any of these.
INNER JOIN
LEFT JOIN
RIGHT JOIN
OUTER JOIN
So I'm retrieving data from the database using odbc. One of my fields, which was causing the problem, is AutoNumber. In my query when I use, '" convert.toint64(empid)"', I get an error of data type missmatch. But when I used parameter, it worked perfectly. Can someone tell me what is the difference. As far as I know, AutoNumber is a long integer and long int is 64, right?
here are both of my queries:
string cmdText = "SELECT p.projID, p.projName, a.wageperday " +
"FROM ((projects p INNER JOIN assigns a ON p.projID = a.projname) " +
"INNER JOIN empos e ON a.employeeID= e.ID) " +
"WHERE a.employeeID = ?";
OdbcCommand assignslist = new OdbcCommand(cmdText, _connection);
assignslist.Parameters.AddWithValue("#empID", empid);
OdbcDataReader readassigns = assignslist.ExecuteReader();
GridView1.DataSource = readassigns;
GridView1.DataBind();
(this one works fine)
string cmdText = "SELECT p.projID, p.projName, a.wageperday " +
"FROM ((projects p INNER JOIN assigns a ON p.projID = a.projname) " +
"INNER JOIN empos e ON a.employeeID= e.ID) " +
"WHERE a.employeeID = '" + convert.toint64( empid ) + "';
OdbcCommand assignslist = new OdbcCommand(cmdText, _connection);
OdbcDataReader readassigns = assignslist.ExecuteReader();
GridView1.DataSource = readassigns;
GridView1.DataBind();
for this one, i get an error even if I removed the conversion, I get an error.
One more question, I don't understand INNER JOIN perfectly and the above code was from a user here who helped me. I don't understand why did he use "FROM ((projects p INNER JOIN assigns a ON p.projID = a.projname) " +
"INNER JOIN empos e ON a.employeeID= e.ID)"
two brackets -- I mean a bracket inside a bracket. And if I wanna join a 4th or 5th table do I have to put it inside a bracket aside from the main bracket? An example would be much appreciated!
If a.employeeID is a number then your problem are the quotes and the concatenation of a number to a string.
"WHERE a.employeeID = " + convert.toint64(empid).ToString()
but this make no sense because you have a string to build so, you could simply write
"WHERE a.employeeID = " + empid.ToString();
however use always the parameterized query. That is the correct way to go.
A parameterized query allows the Framework code to pass the parameters with the correct format and you don't have to worry about quoting values, format of dates and decimal separators. (And last but not least, you avoid any possibilities of Sql Injection)
For the second part of your question, JOIN is used to put togheter data from two tables, when you have more than one JOIN the parenthesys help to understand how the grouping from the tables are perfomed. First the data from projects and assigns are grouped together following the rules of the INNER JOIN then the resulting set of data is joined with the data from the employee table following the rules of the second join.
In your second query, instead of using convert.toint64( empid ) try using empid.ToString():
"WHERE a.employeeID = " + empid.ToString();
The error you were receiving was due to the fact that you were trying to concatenate a string with an integer.
With regards to the INNER JOINs you are using, the use of the brackets is dependant upon the database you are using. In most cases, you will not need the brackets at all and they can be removed without any issue, so you could rewrite the query to:
string cmdText = "SELECT p.projID, p.projName, a.wageperday " +
"FROM projects p " +
"INNER JOIN assigns a ON p.projID = a.projname " +
"INNER JOIN empos e ON a.employeeID = e.ID " +
"WHERE a.employeeID = " empid.ToString();
You're trying to add a string and an integer, which isn't allowed automatically. You'd have to convert the number to a string first, like this:
"WHERE a.employeeID = '" + empid.ToString() + "';
But, using parameters is the better way for other reasons (best habit to be in, to avoid SQL-injection attacks, etc.).
Here's what needs to be done:
Match 2 fields from different tables in SQL Server( done ), update fields in table1 where table1.field1 = table2.field2 (problem, it just updates all the records in the table)
Here's what I have , where tempTableName is a table imported to SQL Server for the purpose of the query:
"UPDATE Table1 SET Table1.fieldN ='" + DateTime.Now.DayOfYear + "' FROM " + tempTableName + " CROSS JOIN Table1 WHERE (" + tempTableName + ".fieldX = Table1.fieldY)"
Here's what I've figured out:
everything after the FROM is useless as far as actual functionality is concerned, it runs the query but the results are not "linked" in any way to the actual UPDATE statement
To sum up :
The query I've figured out updates all records in table1, I need the query to update only the rows matched by the query after FROM
PS. Forgive me if this seems trivial and that I haven't done research but the fact of the matter is that 2 weeks ago I'd never even heard of SQL and have relied heavily on SO for direction and advice.
Your CROSS JOIN should be an INNER JOIN instead.
"UPDATE t1
SET fieldN ='" + DateTime.Now.DayOfYear + "'
FROM " + tempTableName + " t2 INNER JOIN Table1 t1 ON t1.fieldy = t2.fieldx"