Oracle Key Concepts - Make Sure You Know All!
The content taken from
Title: Oracle Database Administration Concepts &
Implementation Made Simple
ISBN: 0-9770739-0-4
Author: Asim Abbasi
Oracle Key Concepts - Make Sure You Know All!
81. Outer join will give you all the records from the first table and
only those records from the second table where there is a join.
82. Positive sign (+) will be placed with the column of the table having
least number of records, in the WHERE clause.
83. If you forget to mention the WHERE clause in the UPDATE statement,
all the values in that column will get update.
84. While inserting new values in the table the order of columns should
be kept in mind otherwise you may get a type mismatch error. To avoid
this try using the INSERT syntax where you have to specify the column
names.
85. Each user we create in Oracle is considered as a Schema.
86. Each object created by user lies under his/her schema.
87. DBA is the owner of all the schemas and hence all the objects within
each of these schemas.
88. Certain modifications using ALTER TABLE statement are not possible
if you are already having the data inside that table.
89. One way of getting rid of unwanted column or unwanted data is to
utilize the power of CREATE TABLE AS statement.
90. Each value in the Primary Key column is a unique identifier for the
whole record/row or in other words, no duplicate or NULL values are
allowed in Primary key constraint column.
91. Oracle creates a implicit index for a column having Primary key
constraint on it.
92. Index helps in speeding up the search process just like the index at
the end of a book.
93. Referential Integrity constraint also known as PRIMARY/FOREIGN KEY
relationship between two or more tables results in two thing
94. Cannot delete any record from parent table with related PRIMARY KEY
column value in child table’s FOREIGN KEY column unless we use ON DELETE
CASCADE clause.
95. Cannot update/insert anything in child’s table FOREIGN KEY column
with no corresponding value in parent table PRIMARY KEY column
96. Having a clear concept about the following two terms is really
essential because these two terms are widely used in all RDBMS.
97. Many author uses these terms a lot keeping in their mind that the
read knows it’s meaning already.
98. Joins statements can be executed on tables having Referential
Integrity constraint or not.
99. The word “Join” should not be confused with as I if you are joining
the two tables permanently.
100. Once you drop a VIEW, base tables and views will not get deleted.
Oracle Key Concepts - Make Sure You Know All!
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