Gbase8s database type

        SQL The database type specifies the value range of an attribute . The data type directly corresponds to the concept of domain in the relational model . Each attribute in the relationship must come from a domain . Accordingly , The value of each column in the table must conform to the data type specified when defining the table . The data type is shown in the following figure ：

Common data types and descriptions are as follows ：

Numerical type （Numeric）         INTEGER/INT         SERIAL         SERIAL8         SMALLINT         BIGINT         BIGSERIAL         DECIMAL NUMERIC(p,s)         REAL or SMALLFLOAT         FLOAT         DOUBLE PRECISION         Money(p,s) Time type （TIME）         DATE         DATETIME         INTERVAL

Character （CHARACTER）         CHAR(n)         CHARACTER VARYING(n,r)         VARCHAR(n,r)         LVARCHAR(n)         NCHAR(n)         NVARCHAR(m,r) Big object （Large Objects）         BYTE         TEXT         BLOB         CLOB Boolean type （BOOLEAN）         BOOLEAN

1. value type

（1）INTEGER/INT

        4 Bytes , by -（231-1） To 231-1  The integer of .

（2）INT8 or BIGINT

        8 Bytes , by -（263-1） To 263-1 The integer of .

（3）BIGINT

        be better than INT8.

（4）SMALLINT

        2 Bytes , by -（215-1） To 215-1  The integer of .

（5）SERIAL

        4 Bytes , by 1 To 231-1 The positive integer , Automatically incremented by the server .

（6）SERIAL8 or  BIGSERIAL

        8 Bytes , by 1 To 263-1 The positive integer , Automatically incremented by the server .

（7）BIGSERIAL

        be better than SERIAL8.

（8）FLOAT or DOUBLE PRECISION

        Double precision floating point , Yes 16 A significant .

（9）SMALLFLAOT or REAL

        Single-precision floating-point , Yes 8 A significant .

（10）DECIMAL(p,s) or NUMERIC(p,s)

        Fixed point decimals , Among them p It's the total number of digits ,s It's the number of digits to the right of the decimal point .

（11）MONEY(p,s)

        Monetary value , And DECIMAL be similar , Format with currency characters .

2. Character type

（1）CHAR(n)/CHARACTER(n)

        Fixed length string ,n Is the length of a string , The default is 1 byte . If the length is less than n, Then fill in the blanks to n Characters .n The maximum value of is 32767.

（2）VARCHAR(n,r)/CHARACTERVARYING(n,r)

        Variable length string ,n Is the maximum byte length ,r Is the minimum reserved space ; If the length of the stored value is less than r, Then fill in the blanks to r Characters ; If the length of the stored value is greater than r But less than n, Then it only takes up the space needed to store data .n The maximum value of is 255.

（3）LVARCHAR(n)

        Variable length string ,n Is the maximum byte length , The default is 2048 byte . Use only the space needed to store data ,n The maximum value of is 32739.

（4）NCHAR(n)

        Fixed length string , Including the use of  Global Language Support（GLS） Store single byte and multi byte character sets determined by the database region ; Local collation order is also allowed .

（5）NVARCHAR(n,r)

        Variable length string , The meaning of parameter is the same as VARCHAR, Have and NCHAR Similar special properties .

        How to choose char  perhaps varchar ？

        char(1) Occupy 1 byte , and Varchar(1) Occupy 2 byte .

        For fixed length, choose char,N<20 And little change in the case of choice char, In particular, you need to create index Field of , You should choose char, Instead of varchar.

3. Time type

（1）Date

        The default format is MM/DD/YY, It can be done by GL_DATE Environment variable modification .

（2）DATETIME

        Date time , The default format is YYYY-MM-DD HH:MM:SS:FFF, Can pass GL_DATETIME Modify the format of environment variables ：

    Datetime year to second,
    Datetime year to fraction(5),

（3）INTERVAL

        time span , Format and DATETIME identical .

4. Big object

        Simple large objects have the following types .

（1）BYTE

        The maximum is 2GB.

（2）TEXT

        The maximum is 2GB.

        Intelligent large objects have the following types .

        <1> BLOB Binary big object , The maximum is 4TB, Used to store binary data .

        <2> CLOB Character large object , The maximum is 4TB, For text data .

5. Boolean type

BOOLEAN：'t'  or  'f'.