Recommended Use of Data Types in Databases
Recommended Use of Types in Qt Supported Databases
This table shows the recommended data types used when extracting data from the databases supported in Qt. It is important to note that the types used in Qt are not necessarily valid as input to the specific database. One example could be that a double would work perfectly as input for floating point records in a database, but not necessarily as a storage format for output from the database since it would be stored with 64-bit precision in C++.
IBM DB2 Data Types
| IBM DB2 data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| SMALLINT | 16-bit signed integer | typedef qint16 |
| INTEGER | 32-bit signed integer | typedef qint32 |
| BIGINT | 64-bit signed integer | typedef qint64 |
| REAL | 32-bit Single-precision floating point | By default mapping to QString |
| DOUBLE PRECISION | 64-bit Double-precision floating point | By default mapping to QString |
| FLOAT | 64-bit Double-precision floating point | By default mapping to QString |
| CHAR | Fixed-length, null-terminated character string | Mapped to QString |
| VARCHAR | Null-terminated varying length string | Mapped to QString |
| LONG VARCHAR | Not null-terminated varying length character string | Mapped to QString |
| BLOB | Not null-terminated varying binary string with 4-byte string length indicator | Mapped to QByteArray |
| CLOB | Character large string object | Mapped to QString |
| DATE | Null-terminated character string of the following format: yyyy-mm-dd | Mapped to QDate |
| TIME | Null-terminated character string of the following format: hh.mm.ss | Mapped to QTime |
| TIMESTAMP | Null-terminated character string of the following format: yyyy-mm-dd-hh.mm.ss.nnnnnn | Mapped to QDateTime |
Borland InterBase Data Types
| Borland InterBase data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| BOOLEAN | Boolean | bool |
| TINYINT | 8 bit signed integer | typedef qint8 |
| SMALLINT | 16-bit signed integer | typedef qint16 |
| INTEGER | 32-bit signed integer | typedef qint32 |
| BIGINT LONG | 64-bit signed integer | typedef qint64 |
| REAL FLOAT | 32-bit floating point | By default mapping to QString |
| FLOAT | 64-bit floating point | By default mapping to QString |
| DOUBLE | 64-bit floating point | By default mapping to QString |
| DOUBLE PRECISION | 64-bit Double-precision floating point | By default mapping to QString |
| VARCHAR STRING | Character string, Unicode | Mapped to QString |
| CLOB | Character large string object | Mapped to QString |
| DATE | Displays date. Format: 'yyyy-mm-dd' | Mapped to QDate |
| TIME | Displays time. Format is 'hh:mm:ss' in 24-hour format | Mapped to QTime |
| TIMESTAMP | Displays a timestamp. Format is 'yyyy-mm-dd hh:mm:ss' | Mapped to QDateTime |
MySQL Data Types
| MySQL data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| TINYINT | 8 bit signed integer | typedef qint8 |
| TINYINT UNSIGNED | 8 bit unsigned integer | typedef quint8 |
| SMALLINT | 16-bit signed integer | typedef qint16 |
| SMALLINT UNSIGNED | 16-bit unsigned integer | typedef quint16 |
| INT | 32-bit signed integer | typedef qint32 |
| INT UNSIGNED | 32-bit unsigned integer | typedef quint32 |
| BIGINT | 64-bit signed integer | typedef qint64 |
| FLOAT | 32-bit Floating Point | By default mapping to QString |
| DOUBLE | 64-bit Floating Point | By default mapping to QString |
| CHAR | Character string | Mapped to QString |
| VARCHAR | Character string | Mapped to QString |
| TINYTEXT | Character string | Mapped to QString |
| TEXT | Character string | Mapped to QString |
| MEDIUMTEXT | Character string | Mapped to QString |
| LONGTEXT | Character string | Mapped to QString |
| CLOB | Character large string object | Mapped to QString |
| all BLOB types | BLOB | Mapped to QByteArray |
| DATE | Date without Time | Mapped to QDate |
| DATETIME | Date and Time | Mapped to QDateTime |
| TIMESTAMP | Date and Time | Mapped to QDateTime |
| TIME | Time | Mapped to QTime |
| YEAR | Year (int) | Mapped to QDateTime |
| ENUM | Enumeration of Value Set | Mapped to QString |
Oracle Call Interface Data Types
| Oracle Call Interface data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| NUMBER | FLOAT, DOUBLE, PRECISIONc REAL | By default mapping to QString |
| NUMBER(38) | INTEGER INT SMALLINT | typedef qint8/16/32/64 |
| NUMBER(p,s) | NUMERIC(p,s) DECIMAL(p,s)a | By default mapping to QString |
| NVARCHAR2(n) | Character string (NATIONAL CHARACTER VARYING(n) NATIONAL CHAR VARYING(n) NCHAR VARYING(n)) | Mapped to QString |
| NCHAR(n) | Character string (NATIONAL CHARACTER(n) NATIONAL CHAR(n) NCHAR(n)) | Mapped to QString |
| CHAR(n) | Character string (CHARACTER(n) CHAR(n)) | Mapped to QString |
| CLOB | Character large string object | Mapped to QString |
| BLOB | A binary large object | Mapped to QByteArray |
| TIMESTAMP | Year, month, and day values of date, as well as hour, minute, and second values of time | Mapped to QDateTime |
ODBC Data Types
| ODBC data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| BIT | Boolean | BOOL |
| TINYINT | 8 bit integer | typedef qint8 |
| SMALLINT | 16-bit signed integer | typedef qint16 |
| INTEGER | 32-bit signed integer | typedef qint32 |
| BIGINT | 64-bit signed integer | typedef qint64 |
| REAL | 32-bit Single-precision floating point | By default mapping to QString |
| FLOAT | 64-bit Double floating point | By default mapping to QString |
| DOUBLE | 64-bit Double floating point | By default mapping to QString |
| CHAR | Character string | Mapped to QString |
| VARCHAR | Character string | Mapped to QString |
| LONGVARCHAR | Character string | Mapped to QString |
| CLOB | Character large string object | Mapped to QString |
| DATE | Character string | Mapped to QDate |
| TIME | Character Time, Character string | Mapped to QTime |
| TIMESTAMP | Character Time, Character string | Mapped to QDateTime |
PostgreSQL Data Types
| PostgreSQL data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| BOOLEAN | Boolean | bool |
| SMALLINT | 16-bit signed integer | typedef qint16 |
| INTEGER | 32-bit signed integer | typedef qint32 |
| BIGINT | 64-bit signed integer | typedef qint64 |
| REAL | 32-bit variable-precision floating point | By default mapping to QString |
| DOUBLE PRECISION | 64-bit variable-precision floating point | By default mapping to QString |
| DECIMAL VARIABLE | user-specified precision, exact | Mapped to QString |
| NUMERIC VARIABLE | user-specified precision, exact | Mapped to QString |
| VARCHAR | variable-length character string | Mapped to QString |
| CHARACTER | Character string of fixed-length | Mapped to QString |
| TEXT | Character string of variable-length | Mapped to QString |
| CLOB | Character large string object | Mapped to QString |
| TIMESTAMP | 8 bytes, both date and time | Mapped to QDateTime |
| TIMESTAMP | 8 bytes, both date and time, with time zone | Mapped to QDateTime |
| DATE | 4 bytes, dates only | Mapped to QDate |
| TIME | 8 bytes, times of day only 00:00:00.00 - 23:59:59.99 | Mapped to QTime |
| TIME | 12 bytes times of day only, with time zone 00:00:00.00+12 | Mapped to QDateTime |
QSQLITE SQLite version 3 Data Types
| QSQLITE SQLite version 3 data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| NULL | NULL value. | NULL |
| INTEGER | Signed integer, stored in 8, 16, 24, 32, 48, or 64-bits depending on the magnitude of the value. | typedef qint8/16/32/64 |
| REAL | 64-bit floating point value. | By default mapping to QString |
| TEXT | Character string (UTF-8, UTF-16BE or UTF-16-LE). | Mapped to QString |
| CLOB | Character large string object | Mapped to QString |
| BLOB | The value is a BLOB of data, stored exactly as it was input. | Mapped to QByteArray |
Sybase Adaptive Server Data Types
| Sybase Adaptive Server data type | SQL type description | Recommended input (C++ or Qt data type) |
|---|
| BINARY | Describes a fixed-length binary value up to 255 bytes in size. | Mapped to QByteArray |
| CHAR | Character String | Mapped to QString |
| DATETIME | Date and time. Range: 1753-01-01 00:00:00 through 9999-12-31 23:59:59. | Mapped to QDateTime |
| NCHAR | Character String of fixed length | Mapped to QString |
| NVARACHAR | Character String of variable length | Mapped to QString |
| VARCHAR | Character String of fixed length | Mapped to QString |
| CLOB | Character large string object | Mapped to QString |
| TIMESTAMP | A unique number within a database | Mapped to QString |
| SMALLDATETIME | Date and time. Range: 1900-01-01 00:00 through 2079-12-31 23:59 | Mapped to QDateTime |
| UNICHAR | Character String of fixed length.(Unicode) | Mapped to QString |
| UNIVARCHAR | Character String of variable length.(Unicode) | Mapped to QString |
| VARBINARY | Describes a variable-length binary value up to 255 bytes in size | Mapped to QByteArray |
SQLite Version 2
SQLite version 2 is "typeless". This means that you can store any kind of data you want in any column of any table, regardless of the declared data type of that column. We recommend that you map the data to QString.
|
|
Best Of
Actualités les plus lues
Le blog Digia au hasard
Le blog Digia est l'endroit privilégié pour la communication sur l'édition commerciale de Qt, où des réponses publiques sont apportées aux questions les plus posées au support. Lire l'article.
Communauté
Ressources
Liens utiles
Contact
- Vous souhaitez rejoindre la rédaction ou proposer un tutoriel, une traduction, une question... ? Postez dans le forum Contribuez ou contactez-nous par MP ou par email (voir en bas de page).
Qt dans le magazine
|
