This article
will show you on how to get a data with one or more entities/table are involve.
ok let’s do the basic. Given that we have table of products and table of sales
and with this respective contents when we want to view all of the products that
can be sold we can use this SQL statement:
Select *
From tbl_products
The
keyword select is used to instruct on what are the specific fields/attributes
to be shown when this statement is
executed, the * symbol indicates that you want to select all the fields on that table but if you want
to select/get a specific column you will just need to specify on what is the
name of that column separated by comma if it is multiple fields.
Select fld_PID,fld_ProductName
From tbl_Products
The
“from” clause is used to specify on what is the name of table you want to
access multiple tables can be declared on the from clause separating it by
comma.
Select *
From tbl_Sales,
tbl_products
This
select statement will just show the following results:
If
you observe the result it just select the two tables and merge it and repeated
the content we don’t like this result hmmmm so what do we want to do?, we want
to see on what are the products which are already sold. Using the where clause we can use a certain
query to show it.
Select tbl_Products.fld_PID, tbl_Products.fld_productname, tbl_Sales.fld_Quantity,tbl_Sales.fld_Date
From tbl_Products,tbl_Sales
Where tbl_Products.fld_PID = tbl_Sales.fld_PID
That
is an example of selecting one record to another table. There are more basic
way in selecting a record from two table or more, using what we call the inner
join and outer join , but for this simple purpose of demonstration you can use
this way of selecting a record, take note that where clause is used to select a
record with specific criteria or condition.
If
you want to access a field using two table u need to specify the name of the
table then put a dot after that the name of the field, tbl_Products.fld_productname to make your statement shorter you can
use some technique called Alias.
NOTE:
if you already read the article of creating a recordset to your vb6 project you
can put this statement on the rst.open part.
Happy coding
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