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Data Type (data_type) Locate the document in the library structure

A column definition (column_definition) can contain both  column_name  and data types.

The following data types can be distinguished:

·        NULL value

·        Special NULL value

·        Non-NULL value
Character String, LONG Column, Number, Date Value, Time Value, Time Stamp Value, BOOLEAN

Non-NULL values can be specified using the syntax element data_type .

Syntax

<data_type> ::=
  CHAR[ACTER] [(<unsigned_integer>)] [ASCII | BYTE | UNICODE]
| VARCHAR [(<unsigned_integer>)] [ASCII | BYTE | UNICODE]
| LONG [VARCHAR] [ASCII | BYTE | UNICODE]
| BOOLEAN
| FIXED (<unsigned_integer> [,<unsigned_integer>])
| FLOAT (<unsigned_integer>)
| INT[EGER] | SMALLINT
| DATE | TIME | TIMESTAMP

A code attribute can also be specified for the following character strings (ASCII, BYTE, or UNICODE) as part of a column_definition if necessary: CHAR[ACTER], VARCHAR, LONG[VARCHAR]

Examples

SQL Tutorial, Tables, Number Generator for a Single Column of a Table

Explanation

In addition to the data types defined above, the following data types are also permitted in a column definition. The table below also indicates the way these are mapped to the above-mentioned data types.

Data Type

Is Mapped To

BINARY(p)

FIXED(p)

DEC[IMAL](p,s)

FIXED(p,s)

DEC[IMAL](p)

FIXED(p)

DEC[IMAL]

FIXED(5)

DOUBLE PRECISION

FLOAT(38)

FLOAT

FLOAT(16)

FLOAT(39..64)

FLOAT(38)

LONG VARCHAR

LONG

NUMERIC(p,s)

FIXED(p,s)

NUMERIC(p)

FIXED(p)

NUMERIC

FIXED(5)

REAL(p)

FLOAT(p)

REAL

FLOAT(16)

SERIAL

FIXED(10) DEFAULT SERIAL

SERIAL(p)

FIXED(10) DEFAULT SERIAL(p)

Memory Requirements of a Column Value According to Data Type

Note that, in the column definition (column_definition), the memory requirement of a column value depends on the data type. You can get a rough idea of the memory requirement using the following table.  Please note that these values are intended as guidance values and are applicable in most cases but may vary depending on your system configuration.

Data Type

Memory Requirements of a Column Value in Bytes for Data Type

FIXED(p,s)

(p+1) DIV 2 + 2

FLOAT(p)

(p+1) DIV 2 + 2

BOOLEAN

2

DATE

9

TIME

9

TIMESTAMP

21

LONG

9

CHAR(n); n<=30

n+1

CHAR(n); 30<n<=1023; key column

n+1

CHAR(n); 30<n<=254; no key column

n+2

CHAR(n);  254<n; no key column

n+3

CHAR(n) UNICODE; n<=15

2*n+1

CHAR(n) UNICODE; 15<n<=511; key column

2*n+1

CHAR(n) UNICODE; 15<n<=127; no key column

2*n+2

CHAR(n) UNICODE; 127<n; no key column

2*n+3

VARCHAR(n); n<=1023; key column

n+1

VARCHAR(n); n<=254; no key column

n+2

VARCHAR(n); 254<n; no key column

n+3

VARCHAR(n) UNICODE; n<=511; key column

2*n+1

VARCHAR(n) UNICODE; n<=127; no key column

2*n+2

VARCHAR(n) UNICODE; 127<n; no key column

2*n+3

 

 

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