Chapter VI data type (V)

Chapter six data type （ 5、 ... and ）

Integer code of data type

In query metadata and other contexts , The data type defined for the column can be returned as an integer code . CType（ Client data type ） Integer codes are listed in %SQL.StatementColumnclientType Properties of the .

ODBC and JDBC Use xDBC Data type code (SQLType). ODBC The data type code is defined by %SQL.Statement.%Metadata.columns.GetAt() Method returns , As shown in the example above . SQL Shell Metadata also returns ODBC Data type code . JDBC Code and the ODBC Same code , In addition to the representation of time and date data types . These are listed below ODBC and JDBC value ：

ODBC	JDBC	Data Type
-11	-11	GUID
-7	-7	BIT
-6	-6	TINYINT
-5	-5	BIGINT
-4	-4	LONGVARBINARY
-3	-3	VARBINARY
-2	-2	BINARY
-1	-1	LONGVARCHAR
0	0	Unknown type
1	1	CHAR
2	2	NUMERIC
3	3	DECIMAL
4	4	INTEGER
5	5	SMALLINT
6	6	FLOAT
7	7	REAL
8	8	DOUBLE
9	91	DATE
10	92	TIME
11	93	TIMESTAMP
12	12	VARCHAR

IRIS It also supports the use of multi byte character sets ODBC Application's Unicode SQL type , For example, Chinese 、 Hebrew 、 Japanese or Korean language environment .

ODBC	Data Type
-10	WLONGVARCHAR
-9	WVARCHAR

Create user defined DDL data type

You can modify the data type set by overriding the data type mapping of the system data type parameter value or defining a new user data type . The system data type can be modified to override Default mapping . You can create user-defined data types to provide Other data type mappings not provided .

To view and modify or add to the current user data type mapping , Please go to the administration portal , Choose system management 、 To configure 、SQL And object settings 、 user DDL mapping . To add a user data type , Please select to create a new user-defined DDL mapping . In the displayed box , Enter a name , for example VARCHAR(100) And data types , for example MyString100(MAXLEN=100).

The result will be user-defined DDL An entry in the data type list .

User defined data types can be created as data type classes . for example , You may want to create a maximum of 10 Character string data type , Then truncate the rest of the input data . This data type will be created Sample.TruncStr, As shown below ：

Class Sample.TruncStr Extends %Library.String
  {
  Parameter MAXLEN=10;
  Parameter TRUNCATE=1;
  }

To use this data type in a table definition , Just specify the data type class name ：

CREATE TABLE Sample.ShortNames (Name Sample.TruncStr)

As shown in the previous example , There are several useful routines for entering user-defined DDL data type ：

• maxval^%apiSQL() — Given precision and scale , Return each IRIS The maximum valid value of a numeric data type (MAXVAL). Grammar is ：

     maxval^%apiSQL(precision,scale)

• minval^%apiSQL() — Given precision and scale , Return each IRIS The least significant value of a numeric data type (MINVAL). Grammar is ：

     minval^%apiSQL(precision,scale)

If necessary DDL The data type maps to a collection type of Stream Of IRIS attribute , Please specify... For character stream data %Stream.GlobalCharacter, Specify... For binary stream data %Stream.GlobalBinary.

If you can't find it DDL mapping , Then pass on

If DDL Encountered not in SystemDataTypes Tabular DDL Data types in the data type column , It then checks UserDataTypes surface . If there is no mapping for any data type in any table , No data type conversion will occur , And the data type will be passed directly to DDL Class definitions specified in .

for example , The following field definitions may appear in DDL In the sentence ：

     CREATE TABLE TestTable (
          Field1 %String,
          Field2 %String(MAXLEN=45)
          )

In view of the above definition , If DDL stay SystemDataTypes or UserDataTypes I can't find it in China. %String or %String(MAXLEN=%1) or %String(MAXLEN=45) Mapping , Then pass on %String and %String(MAXLEN=45) Type directly to the appropriate class definition .

Convert data type

To convert data from one data type to another , Please use CAST or CONVERT function .

CAST Support conversion to multiple string and numeric data types , as well as DATE、TIME as well as TIMESTAMP and POSIXTIME Timestamp data type .

CONVERT There are two forms of grammar . Both forms support and DATE、TIME as well as TIMESTAMP and POSIXTIME Conversion between timestamp data types , And other data types .

VARCHAR Of CAST and CONVERT Handle

VARCHAR data type （ No size specified ） Mapping to 1 A character MAXLEN, As shown in the table above . however , When CAST or CONVERT Convert the value to VARCHAR when , The default size mapping is 30 Characters . Provide this 30 The default size of characters is for non - IRIS The software requires compatibility .