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81. What Are The Data Types Allowed In A Table?
Date Posted: 07/03/2012
Ans: When ON DELETE CASCADE is specified Oracle maintains referential integrity by automatically removing dependent foreign key values if a referenced primary or unique key value is removed.
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82. How Many LONG Columns Are Allowed In A Table? Is It Possible To Use LONG Columns In WHERE Clause Or ORDER BY?
Date Posted: 07/03/2012
Ans: Only one LONG column is allowed. It is not possible to use LONG column in WHERE or ORDER BY clause.
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83. What Are The Pre-requisites To Modify Data Type Of A Column And To Add A Column With NOT NULL Constraint?
Date Posted: 07/03/2012
Ans:
To modify the data type of a column the column must be empty.
To add a column with NOT NULL constrain, the table must be empty.
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84. Where The Integrity Constraints Are Stored In Data Dictionary?
Date Posted: 07/03/2012
Ans: The integrity constraints are stored in USER_CONSTRAINTS.
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85. How Will You Activate/deactivate Integrity Constraints?
Date Posted: 07/03/2012
Ans: The integrity constraints can be enabled or disabled by ALTER TABLE ENABLE CONSTRAINT / DISABLE CONSTRAINT.
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86. If Unique Key Constraint On DATE Column Is Created, Will It Validate The Rows That Are Inserted With SYSDATE?
Date Posted: 07/03/2012
Ans: It won’t, Because SYSDATE format contains time attached with it.
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87. What Is A Database Link?
Date Posted: 07/03/2012
Ans: Database link is a named path through which a remote database can be accessed.
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88. How To Access The Current Value And Next Value From A Sequence? Is It Possible To Access The Current Value In A Session Before Accessing Next Value?
Date Posted: 07/03/2012
Ans: Sequence name CURRVAL, sequence name NEXTVAL. It is not possible. Only if you access next value in the session, current value can be accessed.
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89. Can A View Be Updated/inserted/deleted? If Yes – Under What Conditions?
Date Posted: 07/03/2012
Ans: A View can be updated/deleted/inserted if it has only one base table if the view is based on columns from one or more tables then insert, update and delete is not possible.
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90. What Is The Fastest Way Of Accessing A Row In A Table?
Date Posted: 07/03/2012
Ans: Using ROWID.
CONSTRAINTS
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