Oracle Faq
.
1.What Is SQL?
SQL,
SEQUEL (Structured English Query Language), is a language foRDBMS (Relational
Database Management Systems). SQL was developed by IBM Corporation.
2.How Many Categories of Data Types?
Oracles
supports the following categories of data types:
:-Oracle Built-in Datatypes. :-ANSI, DB2, and SQL/DS Datatypes.
:-User-Defined Types.
:-Oracle-Supplied Types.
3.What Are the Oracle Built-in Data
Types?
There are
20 Oracle built-in data types, divided into 6 groups:
- Character Datatypes - CHAR, NCHAR, NVARCHAR2, VARCHAR2
- Number Datatypes - NUMBER, BINARY_FLOAT, BINARY_DOUBLE
- Long and Row Datatypes - LONG, LONG RAW, RAW
- Datetime Datatypes - DATE, TIMESTAMP, INTERVAL YEAR TO MONTH, INTERVAL DAY TO SECOND
- Large Object Datatypes - BLOB, CLOB, NCLOB, BFILE
- Row ID Datatypes - ROWID, UROWID
4.What Are the Differences between
CHAR and NCHAR?
Both CHAR
and NCHAR are fixed length character data types. But they have the following
differences:
- CHAR's size is specified in bytes by default.
- NCHAR's size is specified in characters by default. A character could be 1 byte to 4 bytes long depending on the character set used.
- NCHAR stores characters in Unicode.
5.What Are the Differences between
CHAR and VARCHAR2?
The main
differences between CHAR and VARCHAR2 are:
- CHAR stores values in fixed lengths. Values are padded with space characters to match the specified length.
- VARCHAR2 stores values in variable lengths. Values are not padded with any characters.
6.What Are the Differences between
NUMBER and BINARY_FLOAT?
The main
differences between NUMBER and BINARY_FLOAT are:
- NUMBER stores values as fixed-point numbers using 1 to 22 bytes.
- BINARY_FLOAT stores values as single precision floating-point numbers.
7.What Are the Differences between
DATE and TIMESTAMP?
The main
differences between DATE and TIMESTAMP are:
- DATE stores values as century, year, month, date, hour, minute, and second.
- TIMESTAMP stores values as year, month, day, hour, minute, second, and fractional seconds.
8.What Are the Differences between
INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND?
The main
differences between INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND are:
- INTERVAL YEAR TO MONTH stores
values as time intervals at the month level.
- INTERVAL DAY TO SECOND stores
values as time intervals at the fractional seconds level.
9.What Are the Differences between
BLOB and CLOB?
The main
differences between BLOB and CLOB are:
- BLOB stores values as LOB
(Large OBject) in bitstreams.
- CLOB stores values as LOB
(Large OBject) in character steams
10.What Are the ANSI Data Types
Supported in Oracle?
The
following ANSI data types are supported in Oracle:
- CHARACTER(n) / CHAR(n)
- CHARACTER VARYING(n) / CHAR
VARYING(n)
- NATIONAL CHARACTER(n) /
NATIONAL CHAR(n) / NCHAR(n)
- NATIONAL CHARACTER VARYING(n) /
NATIONAL CHAR VARYING(n) / NCHAR VARYING(n)
- NUMERIC(p,s)
- DECIMAL(p,s)
- INTEGER / INT
- SMALLINT
- FLOAT
- DOUBLE PRECISION
- REAL
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