QSqlField Class Reference

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

#include <qsqlfield.h>

Collaboration diagram for QSqlField:

Public Types
enum	RequiredStatus { Unknown = -1 , Optional = 0 , Required = 1 }
	Specifies whether the field is required or optional. More...

Public Member Functions
	QSqlField (const QString &fieldName=QString(), QMetaType type=QMetaType(), const QString &tableName=QString())
	QSqlField (const QSqlField &other)
	Constructs a copy of other.
QSqlField &	operator= (const QSqlField &other)
	Sets the field equal to other.
	QSqlField (QSqlField &&other) noexcept=default
	~QSqlField ()
	Destroys the object and frees any allocated resources.
void	swap (QSqlField &other) noexcept
bool	operator== (const QSqlField &other) const
	Returns true if the field is equal to other; otherwise returns false.
bool	operator!= (const QSqlField &other) const
	Returns true if the field is unequal to other; otherwise returns false.
void	setValue (const QVariant &value)
	Sets the value of the field to value.
QVariant	value () const
	Returns the value of the field as a QVariant.
void	setName (const QString &name)
	Sets the name of the field to name.
QString	name () const
	Returns the name of the field.
void	setTableName (const QString &tableName)
	Sets the tableName of the field to table.
QString	tableName () const
	Returns the tableName of the field.
bool	isNull () const
	Returns true if the field's value is NULL; otherwise returns false.
void	setReadOnly (bool readOnly)
	Sets the read only flag of the field's value to readOnly.
bool	isReadOnly () const
	Returns true if the field's value is read-only; otherwise returns false.
void	clear ()
	Clears the value of the field and sets it to NULL.
bool	isAutoValue () const
	Returns true if the value is auto-generated by the database, for example auto-increment primary key values.
QMetaType	metaType () const
	Returns the field's type as stored in the database.
void	setMetaType (QMetaType type)
	Set's the field's variant type to type.
void	setRequiredStatus (RequiredStatus status)
	Sets the required status of this field to required.
void	setRequired (bool required)
	Sets the required status of this field to \l Required if required is true; otherwise sets it to \l Optional.
void	setLength (int fieldLength)
	Sets the field's length to fieldLength.
void	setPrecision (int precision)
	Sets the field's precision.
void	setDefaultValue (const QVariant &value)
	Sets the default value used for this field to value.
void	setSqlType (int type)
void	setGenerated (bool gen)
	Sets the generated state.
void	setAutoValue (bool autoVal)
	Marks the field as an auto-generated value if autoVal is true.
RequiredStatus	requiredStatus () const
	Returns true if this is a required field; otherwise returns false.
int	length () const
	Returns the field's length.
int	precision () const
	Returns the field's precision; this is only meaningful for numeric types.
QVariant	defaultValue () const
	Returns the field's default value (which may be NULL).
int	typeID () const
bool	isGenerated () const
	Returns true if the field is generated; otherwise returns false.
bool	isValid () const
	Returns true if the field's variant type is valid; otherwise returns false.

Detailed Description

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

\inmodule QtSql

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 QVariants. Using an incompatible type is not permitted. For example:

    QSqlField field("age", QMetaType::fromType<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", QMetaType::fromType<int>());
    field.setValue(QString("123"));  // casts QString to int

QSqlField objects are rarely created explicitly in application code. They are usually accessed indirectly through \l{QSqlRecord}s that already contain a list of fields. For example:

    QSqlQuery query;

\dots

    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

Definition at line 18 of file qsqlfield.h.

Member Enumeration Documentation

RequiredStatus

enum QSqlField::RequiredStatus

Specifies whether the field is required or optional.

\value Required The field must be specified when inserting records. \value Optional The fields doesn't have to be specified when inserting records. \value Unknown The database driver couldn't determine whether the field is required or optional.

See also

requiredStatus()

Enumerator
Unknown
Optional
Required

Definition at line 21 of file qsqlfield.h.

Constructor & Destructor Documentation

QSqlField() [1/3]

QSqlField::QSqlField ( const QString &  fieldName = QString(), QMetaType  type = QMetaType(), const QString &  table = QString()  )

explicit

Since

6.0

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Constructs an empty field called fieldName of type type in table.

See also

setRequiredStatus(), setLength(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

Definition at line 127 of file qsqlfield.cpp.

QSqlField() [2/3]

QSqlField::QSqlField ( const QSqlField &  other )

default

Constructs a copy of other.

QSqlField() [3/3]

QSqlField::QSqlField ( QSqlField &&  other )

defaultnoexcept

~QSqlField()

QSqlField::~QSqlField ( )

default

Destroys the object and frees any allocated resources.

Member Function Documentation

clear()

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()

Definition at line 280 of file qsqlfield.cpp.

References isReadOnly(), and QSqlFieldPrivate::type.

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defaultValue()

QVariant QSqlField::defaultValue

(

)

const

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

See also

setDefaultValue(), metaType(), requiredStatus(), length(), precision(), isGenerated()

Definition at line 451 of file qsqlfield.cpp.

References QSqlFieldPrivate::def.

isAutoValue()

bool QSqlField::isAutoValue

(

)

const

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

Note

When using the ODBC driver, due to limitations in the ODBC API, the isAutoValue() field is only populated in a QSqlField resulting from a QSqlRecord obtained by executing a SELECT query. It is false in a QSqlField resulting from a QSqlRecord returned from QSqlDatabase::record() or QSqlDatabase::primaryIndex().

See also

setAutoValue()

Definition at line 527 of file qsqlfield.cpp.

References QSqlFieldPrivate::autoval.

isGenerated()

bool QSqlField::isGenerated

(

)

const

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

See also

setGenerated(), metaType(), requiredStatus(), length(), precision(), defaultValue()

Definition at line 476 of file qsqlfield.cpp.

References QSqlFieldPrivate::gen.

Referenced by QSqlRecord::isGenerated().

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isNull()

bool QSqlField::isNull

(

)

const

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

See also

value()

Definition at line 394 of file qsqlfield.cpp.

Referenced by QDB2Driver::formatValue(), QMYSQLDriver::formatValue(), QODBCDriver::formatValue(), QPSQLDriver::formatValue(), QSqlDriver::formatValue(), and QSqlRecord::isNull().

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isReadOnly()

bool QSqlField::isReadOnly

(

)

const

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

See also

setReadOnly(), metaType(), requiredStatus(), length(), precision(), defaultValue(), isGenerated()

Definition at line 385 of file qsqlfield.cpp.

References QSqlFieldPrivate::ro.

Referenced by clear(), and setValue().

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isValid()

bool QSqlField::isValid

(

)

const

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

Definition at line 485 of file qsqlfield.cpp.

References QMetaType::isValid(), and QSqlFieldPrivate::type.

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length()

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(), metaType(), requiredStatus(), precision(), defaultValue(), isGenerated()

Definition at line 425 of file qsqlfield.cpp.

References QSqlFieldPrivate::len.

metaType()

QMetaType QSqlField::metaType

(

)

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

setMetaType()

Definition at line 337 of file qsqlfield.cpp.

References QSqlFieldPrivate::type.

Referenced by QDB2Driver::formatValue(), QIBaseDriver::formatValue(), QMYSQLDriver::formatValue(), QODBCDriver::formatValue(), QPSQLDriver::formatValue(), QSqlDriver::formatValue(), and QMimerSQLResult::record().

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name()

QString QSqlField::name

(

)

const

Returns the name of the field.

See also

setName()

Definition at line 323 of file qsqlfield.cpp.

References QSqlFieldPrivate::nm.

Referenced by QSqlRecord::fieldName(), QSqlRecord::indexOf(), and setName().

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operator!=()

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

inline

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

Definition at line 34 of file qsqlfield.h.

References operator==(), and other().

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operator=()

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

default

Sets the field equal to other.

operator==()

bool QSqlField::operator==

(

const QSqlField &

other

)

const

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

Definition at line 156 of file qsqlfield.cpp.

References other().

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precision()

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(), metaType(), requiredStatus(), length(), defaultValue(), isGenerated()

Definition at line 440 of file qsqlfield.cpp.

References QSqlFieldPrivate::prec.

Referenced by QMYSQLDriver::formatValue(), and setPrecision().

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requiredStatus()

QSqlField::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(), metaType(), length(), precision(), defaultValue(), isGenerated()

Definition at line 411 of file qsqlfield.cpp.

References QSqlFieldPrivate::req.

setAutoValue()

void QSqlField::setAutoValue

(

bool

autoVal

)

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

See also

isAutoValue()

Definition at line 538 of file qsqlfield.cpp.

References QSqlFieldPrivate::autoval.

Referenced by qGetTableInfo().

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setDefaultValue()

void QSqlField::setDefaultValue

(

const QVariant &

value

)

Sets the default value used for this field to value.

See also

defaultValue(), value(), setMetaType(), setRequiredStatus(), setLength(), setPrecision(), setGenerated(), setReadOnly()

Definition at line 221 of file qsqlfield.cpp.

References QSqlFieldPrivate::def, and value().

Referenced by qGetTableInfo().

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setGenerated()

void QSqlField::setGenerated

(

bool

gen

)

Sets the generated state.

If gen is false, no SQL will be generated for this field; otherwise, Qt classes such as QSqlQueryModel and QSqlTableModel will generate SQL for this field.

See also

isGenerated(), setMetaType(), setRequiredStatus(), setLength(), setPrecision(), setDefaultValue(), setReadOnly()

Definition at line 245 of file qsqlfield.cpp.

References QSqlFieldPrivate::gen.

Referenced by QSqlQueryModel::insertColumns().

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setLength()

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(), setMetaType(), setRequiredStatus(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

Definition at line 197 of file qsqlfield.cpp.

References QSqlFieldPrivate::len.

setMetaType()

void QSqlField::setMetaType

(

QMetaType

type

)

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

See also

metaType(), setRequiredStatus(), setLength(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

Definition at line 348 of file qsqlfield.cpp.

References QSqlFieldPrivate::type.

Referenced by QMimerSQLResult::record().

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setName()

void QSqlField::setName

(

const QString &

name

)

Sets the name of the field to name.

See also

name()

Definition at line 293 of file qsqlfield.cpp.

References name(), and QSqlFieldPrivate::nm.

Referenced by QMimerSQLResult::record().

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setPrecision()

void QSqlField::setPrecision

(

int

precision

)

Sets the field's precision.

This only affects numeric fields.

See also

precision(), setMetaType(), setRequiredStatus(), setLength(), setDefaultValue(), setGenerated(), setReadOnly()

Definition at line 209 of file qsqlfield.cpp.

References QSqlFieldPrivate::prec, and precision().

Referenced by QMimerSQLDriver::record().

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setReadOnly()

void QSqlField::setReadOnly

(

bool

readOnly

)

Sets the read only flag of the field's value to readOnly.

A read-only field cannot have its value set with setValue() and cannot be cleared to NULL with clear().

Definition at line 304 of file qsqlfield.cpp.

References QSqlFieldPrivate::ro.

Referenced by QSqlQueryModel::insertColumns().

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setRequired()

void QSqlField::setRequired ( bool  required )

inline

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

See also

setRequiredStatus(), requiredStatus()

Definition at line 67 of file qsqlfield.h.

References Required.

Referenced by qGetTableInfo(), and QMimerSQLDriver::record().

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setRequiredStatus()

void QSqlField::setRequiredStatus

(

RequiredStatus

required

)

Sets the required status of this field to required.

See also

requiredStatus(), setMetaType(), setLength(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly()

Definition at line 175 of file qsqlfield.cpp.

References QSqlFieldPrivate::req.

setSqlType()

void QSqlField::setSqlType

(

int

type

)

Definition at line 230 of file qsqlfield.cpp.

References QSqlFieldPrivate::tp.

Referenced by QSQLiteResultPrivate::initColumns(), and QMimerSQLResult::record().

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setTableName()

void QSqlField::setTableName

(

const QString &

table

)

Sets the tableName of the field to table.

See also

tableName()

Definition at line 549 of file qsqlfield.cpp.

References QSqlFieldPrivate::table.

Referenced by QDB2Driver::record().

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setValue()

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()

Definition at line 266 of file qsqlfield.cpp.

References isReadOnly(), and value().

Referenced by QSqlField_snippets(), and QMimerSQLResult::record().

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swap()

void QSqlField::swap ( QSqlField &  other )

inlinenoexcept

Definition at line 31 of file qsqlfield.h.

References d, and other().

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tableName()

QString QSqlField::tableName

(

)

const

Returns the tableName of the field.

Note

When using the QPSQL driver, due to limitations in the libpq library, the tableName() field is not populated in a QSqlField resulting from a QSqlRecord obtained by QSqlQuery::record() of a forward-only query.

See also

setTableName()

Definition at line 564 of file qsqlfield.cpp.

References QSqlFieldPrivate::table.

typeID()

int QSqlField::typeID

(

)

const

Returns the type ID for the field.

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

Definition at line 464 of file qsqlfield.cpp.

References QSqlFieldPrivate::tp.

Referenced by QOCIDriver::formatValue().

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value()

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.

Definition at line 37 of file qsqlfield.h.

Referenced by QDB2Driver::formatValue(), QIBaseDriver::formatValue(), QMYSQLDriver::formatValue(), QOCIDriver::formatValue(), QODBCDriver::formatValue(), QPSQLDriver::formatValue(), QSqlDriver::formatValue(), setDefaultValue(), setValue(), and QSqlRecord::value().

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---

The documentation for this class was generated from the following files:

• qtbase/src/sql/kernel/qsqlfield.h
• qtbase/src/sql/kernel/qsqlfield.cpp