The QSqlField class manipulates the fields in SQL database tables and views. More...

Public Types
enum	RequiredStatus

Public Methods
	QSqlField (const QSqlField &other)

	QSqlField (const QString &fieldName=QString (), QVariant::Type type=QVariant::Invalid)

	~QSqlField ()

void	clear ()

QVariant	defaultValue () const

bool	isAutoValue () const

bool	isGenerated () const

bool	isNull () const

bool	isReadOnly () const

bool	isValid () const

int	length () const

QString	name () const

bool	operator!= (const QSqlField &other) const

QSqlField &	operator= (const QSqlField &other)

bool	operator== (const QSqlField &other) const

int	precision () const

RequiredStatus	requiredStatus () const

void	setAutoValue (bool autoVal)

void	setDefaultValue (const QVariant &value)

void	setGenerated (bool gen)

void	setLength (int fieldLength)

void	setName (const QString &name)

void	setPrecision (int precision)

void	setReadOnly (bool readOnly)

void	setRequired (bool status)

void	setRequiredStatus (RequiredStatus status)

void	setType (QVariant::Type type)

void	setValue (const QVariant &value)

QVariant::Type	type () const

QVariant	value () const

Detailed Description

The QSqlField class manipulates the fields in SQL database tables and views. QSqlField represents the characteristics of a single column in a database table or view, such as the data type and column name. A field also contains the value of the database column, which can be viewed or changed.

Field data values are stored as QVariant. Using an incompatible type is not permitted.

QSqlField field("age", QVariant::Int);

field.setValue(QPixmap()); // WRONG

However, the field will attempt to cast certain data types to the field data type where possible:

QSqlField field("age", QVariant::Int);

field.setValue(QString("123")); // casts QString to int

QSqlField objects are rarely created explicitly in application code. They are usually accessed indirectly through QSqlRecords that already contain a list of fields.

QSqlQuery query;
...
QSqlRecord record = query.record();
QSqlField field = record.field("country");

A QSqlField object can provide some meta data about the field, for example, its name(), variant type(), length(), precision(), defaultValue(), typeID(), and its requiredStatus(), isGenerated() and isReadOnly(). The field's data can be checked to see if it isNull(), and its value() retrieved. When editing the data can be set with setValue() or set to NULL with clear().

See also: QSqlRecord

Member Enumeration Documentation

enum QSqlField::RequiredStatus

Specifies whether the field is required or optional.

Constant	Value	Description
`QSqlField::Required`	`1`	Field must be specified when inserting records.
`QSqlField::Optional`	`0`	Field does not have to be specified when inserting records.
`QSqlField::Unknown`	`-1`	Database driver could not determine whether the field is required or optional.

See also: requiredStatus()

Constructor & Destructor Documentation

QSqlField::QSqlField	(	const QString &	fieldName = `QString()`,
		QVariant::Type	type = `QVariant::Invalid`
	)

Constructs an empty field called fieldName of variant type.

See also: setRequiredStatus(), setLength(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

QSqlField::QSqlField ( const QSqlField & other )

Constructs a copy of other.

QSqlField::~QSqlField ( )

Destroys the object and frees any allocated resources.

Method Documentation

void QSqlField::clear ( )

Clears the value of the field and sets it to NULL. If the field is read-only, nothing happens.

See also: setValue(), isReadOnly(), requiredStatus()

QVariant QSqlField::defaultValue ( ) const

Returns the field's default value (which may be NULL).

See also: setDefaultValue(), type(), requiredStatus(), length(), precision(), isGenerated()

bool QSqlField::isAutoValue ( ) const

Returns true if the value is auto-generated by the database, for example auto-increment primary key values.

See also: setAutoValue()

bool QSqlField::isGenerated ( ) const

Returns true if the field is generated, otherwise returns false.

See also: setGenerated(), type(), requiredStatus(), length(), precision(), defaultValue()

bool QSqlField::isNull ( ) const

Returns true if the field's value is NULL, otherwise returns false.

See also: value()

bool QSqlField::isReadOnly ( ) const

Returns true if the field's value is read-only, otherwise returns false.

See also: setReadOnly(), type(), requiredStatus(), length(), precision(), defaultValue(), isGenerated()

bool QSqlField::isValid ( ) const

Returns true if the field's variant type is valid, otherwise returns false.

int QSqlField::length ( ) const

Returns the field's length.

If the returned value is negative, it means that the information is not available from the database.

See also: setLength(), type(), requiredStatus(), precision(), defaultValue(), isGenerated()

QString QSqlField::name ( ) const

Returns the name of the field.

See also: setName()

bool QSqlField::operator!= ( const QSqlField & other ) const

inline

Returns true if the field is unequal to other, otherwise returns false.

QSqlField & QSqlField::operator= ( const QSqlField & other )

Sets the field equal to other.

bool QSqlField::operator== ( const QSqlField & other ) const

Returns true if the field is equal to other, otherwise returns false.

int QSqlField::precision ( ) const

Returns the field's precision; this is only meaningful for numeric types.

If the returned value is negative, it means that the information is not available from the database.

See also: setPrecision(), type(), requiredStatus(), length(), defaultValue(), isGenerated()

RequiredStatus QSqlField::requiredStatus ( ) const

Returns true if this is a required field, otherwise returns false. An INSERT will fail if a required field does not have a value.

See also: setRequiredStatus(), type(), length(), precision(), defaultValue(), isGenerated()

void QSqlField::setAutoValue ( bool autoVal )

Marks the field as an auto-generated value if autoVal is true.

See also: isAutoValue()

void QSqlField::setDefaultValue ( const QVariant & value )

Sets the default value used for this field to value.

See also: defaultValue(), value(), setType(), setRequiredStatus(), setLength(), setPrecision(), setGenerated(), setReadOnly()

void QSqlField::setGenerated ( bool gen )

Sets the generated state. If gen is false, no SQL will be generated for this field, otherwise, CopperSpice classes such as QSqlQueryModel and QSqlTableModel will generate SQL for this field.

See also: isGenerated(), setType(), setRequiredStatus(), setLength(), setPrecision(), setDefaultValue(), setReadOnly()

void QSqlField::setLength ( int fieldLength )

Sets the field's length to fieldLength. For strings this is the maximum number of characters the string can hold; the meaning varies for other types.

See also: length(), setType(), setRequiredStatus(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

void QSqlField::setName ( const QString & name )

Sets the name of the field to name.

See also: name()

void QSqlField::setPrecision ( int precision )

Sets the field's precision. This only affects numeric fields.

See also: precision(), setType(), setRequiredStatus(), setLength(), setDefaultValue(), setGenerated(), setReadOnly()

void QSqlField::setReadOnly ( bool readOnly )

Sets the read only flag of the field's value to readOnly. A read-only field can not have its value set with setValue() and can not be cleared to NULL with clear().

See also: isReadOnly()

void QSqlField::setRequired ( bool status )

inline

Sets the required status of this field to Required if status is true, otherwise sets it to Optional.

See also: setRequiredStatus(), requiredStatus()

void QSqlField::setRequiredStatus ( RequiredStatus status )

Sets the required status of this field to status.

See also: requiredStatus(), setType(), setLength(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

void QSqlField::setType ( QVariant::Type type )

Set's the field's variant type to type.

See also: type(), setRequiredStatus(), setLength(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

void QSqlField::setValue ( const QVariant & value )

Sets the value of the field to value. If the field is read-only (isReadOnly() returns true), nothing happens.

If the data type of value differs from the field's current data type, an attempt is made to cast it to the proper type. This preserves the data type of the field in the case of assignment, e.g. a QString to an integer data type.

To set the value to NULL, use clear().

See also: value(), isReadOnly(), defaultValue()

QVariant::Type QSqlField::type ( ) const

Returns the field's type as stored in the database. Note that the actual value might have a different type, Numerical values that are too large to store in a long int or double are usually stored as strings to prevent precision loss.

See also: setType()

QVariant QSqlField::value ( ) const

inline

Returns the value of the field as a QVariant.

Use isNull() to check if the field's value is NULL.

See also: setValue()

Public Types

Public Methods

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation