Database.TableColumns
From Xojo Documentation
New in 2019r2
Supported for all project types and targets.
Returns a RowSet with information about all the columns (fields) in the specified TableName.
Notes
RowSet
TableColumns returns a RowSet with these columns:
- ColumnName: A string that is the name of the column.
- FieldType: An integer that describes the type of the column (refer to the table below).
- IsPrimary: A boolean that indicates if the column is part of the primary key.
- NotNull: A boolean that indicates if the column can be set to NULL.
- Length: An integer that describes the length of the field (for some text fields), the precision of numeric data (for some numeric fields) or the default value for a field (for SQLite columns).
Data Types
Use the table below to identify the Column Type based on the FieldType Integer (Not all databases use all these types).
| FieldType | Value | Description |
|---|---|---|
| Null | 0 | Denotes the absence of any value, i.e., a missing value. |
| Byte | 1 | Stores the byte representation of a character string. |
| SmallInt | 2 | A numeric data type with no fractional part.
The maximum number of digits is implementation-specific, but is usually less than or equal to INTEGER. SQLite supports 4-byte smallints. If you are using another data source, check the documentation of your data source. |
| Integer | 3 | A numeric data type with no fractional part.
The maximum number of digits is implementation-specific. SQLite supports 8-byte integer columns and the FieldType evaluates to 19 (64-bit integer). |
| Char | 4 | Stores alphabetic data, in which you specify the maximum number of characters for the field, i.e., CHAR (20) for a 20 character field.
If a record contains fewer than the maximum number of characters for the field, the remaining characters will be padded with blanks. |
| Text or VarChar | 5 | Stores alphabetic data, in which the number of characters vary from record to record, but you don't want to pad the unused characters with blanks.
For example, "VARCHAR (20)" specifies a VARCHAR field with a maximum length of 20 characters. |
| Float | 6 | Stores floating-point numeric values with a precision that you specify, i.e., FLOAT (5). |
| Double | 7 | Stores double-precision floating-point numbers. |
| Date | 8 | Stores year, month, and day values of a date in the format YYYY-MM-DD. The year value is four digits; the month and day values are two digits. |
| Time | 9 | Stores hour, minute, and second values of a time in the format HH:MM:SS.
The hours and minutes are two digits. The seconds values is also two digits, may include a optional fractional part, e.g., 09:55:25.248. The default length of the fractional part is zero. |
| TimeStamp | 10 | Stores both date and time information in the format YYYY-MM-DD HH:MM:SS.
The lengths of the components of a TimeStamp are the same as for Time and Date, except that the default length of the fractional part of the time component is six digits rather than zero. If a TimeStamp values has no fractional component, then its length is 19 digits If it has a fractional component, its length is 20 digits, plus the length of the fractional component. |
| Currency | 11 | This is a 64-bit fixed-point number format that holds 15 digits to the left of the decimal point and 4 digits to the right. |
| Boolean | 12 | Stores the values of TRUE or FALSE. |
| Decimal | 13 | Stores a numeric value that can have both an integral and fractional part.
You specify the total number of digits and the number of digits to the right of the decimal place, i.e., DECIMAL (5.2) specifies a decimal field that can contain values up to 999.99. DECIMAL (5) specifies a field that can contain values up to 99,999. |
| Binary | 14 | Stores code, images, and hexadecimal data.
Consult the documentation of your data source for information on the maximum size of a Binary field. |
| Long Text (Blob) | 15 | Stores a text object.
Consult the documentation of your data source for information on the maximum size of a Blob. |
| Long VarBinary
(Blob) |
16 | Stores a binary object.
SQLite supports blobs of up to any size. Furthermore, a blob can be stored in a column of any declared data affinity. If you are using another data source, check the documentation of your data source. |
| MacPICT | 17 | Stores a Macintosh PICT image.
SQLite does not support this data type. Use a Blob to store images. |
| String | 18 | Text up to about 2 billion bytes. The same as VarChar. |
| Int64 | 19 | Stores a 64-bit integer.
Integer fields in SQLite are 64 bits and FieldType returns 19. |
| Unknown | 255 | Unrecognized data type. |
Sample Code
The following code creates a table and then gets the FieldSchema:
Var dbFile As FolderItem
dbFile = New FolderItem("mydb.sqlite")
db = New SQLiteDatabase
db.DatabaseFile = dbFile
Try
db.CreateDatabase
db.Connect
db.ExecuteSQL("CREATE TABLE invoices(id INTEGER, CustID INTEGER, Amount Double, Note TEXT)")
db.CommitTransaction
Var rs As RowSet
rs = db.TableColumns("invoices")
Var columName As String
columName = rs.ColumnAt(0).StringValue
MessageBox("Column: " + columName)
Catch error As IOException
MessageBox("The database could not be created: " + error.Message)
Catch error As DatabaseException
MessageBox("Database error: " + error.Message)
End Try