SQL Compact Database

The values of the variables are saved in a Microsoft SQL Compact database.
Microsoft SQL Server 2005 Compact Edition is a compact database, ideal for embedding in mobile and desktop applications. It offers developers a programming model common with other editions of SQL Server for developing system dedicated and managed applications. This SQL Server requires relatively few resources, but nevertheless provides the necessary functionality for relational databases such as a robust data store, an optimized query processor and reliable, scalable connection functions.

Compatible version: Microsoft Compact SQL Database 3.5

The variable values are saved in the following table structure.

Column name	Data type	Null permitted	Characteristic
ID	bigint	no	IDENTITY(1,1)
Timestamp	datetime	no
Name	ntext	no
ValueType = "Double"
Value	float	no
ValueType = "Bytes"
Value	image	no

An AutoID is generated in the "ID" column. The value in this column is, in other words, always increased by 1. This functionality makes the IDENTITY property possible.
The "Timestamp" column stores the time at which the data record was saved.
The name of the variable is stored in the "Name" column.
The "Value" column stores the value of the variable.

The table is created with the following SQL command:

/* ValueType = "Double"*/
CREATE TABLE myTable(
    ID          bigint IDENTITY(1,1)   NOT NULL,
    Timestamp   datetime               NOT NULL,
    Name        ntext                  NOT NULL,
    Value       float                  NOT NULL
)

/*ValueType = "Bytes"*/
CREATE TABLE myTable(
    ID          bigint IDENTITY(1,1)   NOT NULL,
    Timestamp   datetime               NOT NULL,
    Name        ntext                  NOT NULL,
    Value       image                  NOT NULL
)

E_DBColumnTypes	MS Compact SQL	PLC Control
eDBColumn_BigInt	bigint	T_ULARGE_INTEGER (TcUtilities.lib)
eDBColumn_Integer	integer	DINT
eDBColumn_SmallInt	smallint	INT
eDBColumn_TinyInt	tinyint	SINT
eDBColumn_Bit	bit	BYTE
eDBColumn_Money	money	LREAL
eDBColumn_Float	float	LREAL
eDBColumn_Real	real	REAL
eDBColumn_DateTime	datetime	DT
eDBColumn_NText	ntext	STRING
eDBColumn_NChar	nchar	STRING
eDBColumn_Image	image	ARRAY OF BYTE
eDBColumn_NVarChar	nvarchar	STRING
eDBColumn_Binary	binary	ARRAY OF BYTE
eDBColumn_VarBinary	varbinary	ARRAY OF BYTE

Notice

Compact Flash Card Lifetime

Do not save the database on the Compact Flash Card in case of an embedded system.
Either use the database in RAM, i.e., do not save to the "Hard disk" folder, or save on a network folder. To many write cycles to the Compact Flash Card can shorten its service life.