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Oracle & VB Questions
Posted Date: 22 Nov 2007 Resource Type: Articles/Knowledge Sharing Category: General
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Posted By: priskiselvin Member Level: Bronze
Rating:  Points: 5
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Oracle:
1. What's the maximum size of a row?
8060 bytes. Don't be surprised with questions like 'what is the
maximum number of columns per table'. Check out SQL Server books
online for the page titled: "Maximum Capacity Specifications".
2. What's the difference between a primary key and a unique key?
Both primary key and unique enforce uniqueness of the column on which
they are defined. But by default primary key creates a clustered index
on the column, where are unique creates a nonclustered index by
default. Another major difference is that, primary key doesn't allow
NULLs, but unique key allows one NULL only.
3. Define candidate key, alternate key, composite key.
A candidate key is one that can identify each row of a table uniquely.
Generally a candidate key becomes the primary key of the table. If the
table has more than one candidate key, one of them will become the
primary key, and the rest are called alternate keys.
A key formed by combining at least two or more columns is called
composite key.
4. What's the difference between DELETE TABLE and TRUNCATE TABLE commands?
DELETE TABLE is a logged operation, so the deletion of each row gets
logged in the transaction log, which makes it slow. TRUNCATE TABLE
also deletes all the rows in a table, but it won't log the deletion of
each row, instead it logs the deallocation of the data pages of the
table, which makes it faster. Of course, TRUNCATE TABLE can be rolled
back.
5. What is difference between SQL and SQL*PLUS?...
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SQL is a language to interact with the database........ It has been 'invented' by IBM.
whereas SQL*PLUS is a tool provided by Oracle Corp. to write down your SQL statements......
6. Which datatype is used for storing graphics and image?
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BLOB is generally used to store pictures. It stands for Binary Large Object. The maximum storage limit is 4GB. There is also one limitation using BLOB, you can have only one column of type BLOB.
7. Difference between database triggers and form triggers?
form triggers is fired when an event occurs, for eg, when mouse is clicked, when list item changed, whereas database triggers fires for each DML operations performed on the associated table and it can be at row level or statement level.
VB ques
1. what is the 3 main differences between flexgrid control and db...
________________________________________
Ans :
1. Datagrid is Editable, flexgrid is Diplay only.
2. DBGrid allows full data binding while MSFlexGrid allows read-only binding
3. MSFlex grid is smaller and allows cell merging while Datagrid is larger and does not allow cell merging.
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2. How to register a component?
Ans :
To register component use - run command prompt type: c: regsvr32 nameofcomp
4. Name of the control used to call a windows application
Ans: OLE is the control used to call a windows application.
5. What are the ADO objects? Explain them.
Ans: There are 3 main objects of ADO
(1) Connection - Used to make connection with Database
(2) command - with this we can execyte command like(select* from)
(3) Recordset - The inmemory Representation of records in ADO is known as
RecordSet
6. Which controls can not be placed in MDI?
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The Controls which do not have Align property can't be placed on MDI Form.
E.g., Picturebox only has Align property in Standard Components of VB other controls dont have align property an hence can't be drawn on MDI Form.
7. Which property of menu cannot be set at run time?
Name property cannot set at run time
8. What is ADO, OLEDB & ODBC?
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ODBC : Open Database Connectivity(ODBC) is a windows technology that lets a database client application connect to a external database.
OLEDB : Low level programming interface designed to access a wide variety of data access
Object Linking and Embedding (OLE).
ADO : ActiveX Data Objects, is universal data access framework that encompasses the functionality of DAO.
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