SQLite
This section contains information on the configuration and the data type mapping of SQLite databases. SQLite is an ideal database for embedded applications. This file-based SQL database requires no installation, since it is already integrated in the TwinCAT Database Server. The relational database offers most of the features of SQL databases and supports the commands of the SQL92 standard. The database enables reliable and fast data storage. However, the database does not allow distinction of users. It is therefore particularly suitable for safe storage of variables on the local system.
Declaration in the TwinCAT Database Server Configurator
SQLite database | |
|---|---|
Database Type | Select "SQLite" from the drop-down menu. |
SQLite database file | Enter the name and path of the database. You can also use the browser dialog. If the database does not yet exist, it can be created with the Create button. Corresponding permissions must exist. |
Authentication | An option for logging into the database as a particular user. |
Password | Enter the corresponding password. |
 | Windows CE support The database is also supported by the Windows CE version of the TwinCAT Database Server, but only on devices with ARM processor. The connection can be established locally. |
| TwinCAT/BSD support This database is supported by the TwinCAT Database Server on TwinCAT/BSD. In addition, however, the installation of the package "sqlite3" from the package repository is required for use. |
Data type mapping between DB and PLC
SQLite has five internal basic data types. For more precise interpretation of the data, additional data types are supported, which are listed in the documentation of the database manufacturer.
E_ColumnTypes | SQLite | TwinCAT PLC |
|---|---|---|
BigInt | BIGINT | T_ULARGE_INTEGER (TcUtilities.lib) |
Integer | INT | DINT |
SmallInt | SMALLINT | INT |
TinyInt | TINYINT | BYTE |
Bit_ | BOOLEAN | BOOL |
Money | DOUBLE | LREAL |
Float | FLOAT | LREAL |
Real_ | REAL | REAL |
DateTime | DATETIME | DT |
NText | TEXT | STRING |
NChar | NCHAR | STRING |
Image | BLOB | ARRAY OF BYTE |
NVarChar | NVARCHAR | STRING |
Binary | BLOB | ARRAY OF BYTE |
VarBinary | BLOB | ARRAY OF BYTE |
Special feature: string or binary data types are unlimited in Sqlite. However, the TwinCAT 3 Database Server requires fixed limits, which can be set in the general server settings.
| Incompatible data types It is possible that incompatible data type designations are created in the database by third-party software, which the TwinCAT3 Database Server cannot interpret. In this case it is helpful to use the SQL Query Builder. |
| Data type support This database supports the data type WSTRING. (See WString support) |
Notice | |
Data security In flash memory devices the number of write access operations is limited. The flash memory devices can fail, with a risk of data loss.
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