QSqlField Class

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

List of all members, including inherited members

Public Types

Public Functions

Detailed Description

A QSqlField stands for one column: it has a name(), a type (metaType()), a value() and what the database tells about the column, such as requiredStatus(), length() and defaultValue(). Fields are mostly met as the parts of a QSqlRecord.

QSqlField field("age", QMetaType::fromType<int>());
field.setValue(42);
field.isNull();   // false
field.clear();
field.isNull();   // true

A read-only field ignores setValue() and clear(). setGenerated() tells QSqlTableModel and QSqlDriver::sqlStatement() whether the field takes part in the SQL they generate.

See also QSqlRecord.

Differences from Qt

Member Type Documentation

enum QSqlField::RequiredStatus

Whether a field must have a value when a row is inserted.

Member Function Documentation

[explicit] QSqlField::QSqlField(const QString &fieldName = QString(), QMetaType type = QMetaType(), const QString &tableName = QString())

Constructs a field named fieldName of the type type that belongs to the table tableName. The value of the field is null.

void QSqlField::clear()

Sets the value of the field to a null value of the type of the field. Nothing happens if the field is read-only.

See also isNull() and setValue().

QVariant QSqlField::defaultValue() const

Returns the value that the database gives the field when a row is inserted without one.

See also setDefaultValue().

bool QSqlField::isAutoValue() const

Returns true if the database gives the field its value, as for an auto-incremented key; otherwise returns false.

See also setAutoValue().

bool QSqlField::isGenerated() const

Returns true if the field takes part in generated SQL statements, which is the default; otherwise returns false.

See also setGenerated().

bool QSqlField::isNull() const

Returns true if the value of the field is null; otherwise returns false.

See also clear().

bool QSqlField::isReadOnly() const

Returns true if the value of the field cannot be changed; otherwise returns false.

See also setReadOnly().

bool QSqlField::isValid() const

Returns true if the field has a valid type; otherwise returns false.

int QSqlField::length() const

Returns the length of the field, or a negative number if the database does not tell.

See also setLength().

QMetaType QSqlField::metaType() const

Returns the type of the field in the database.

See also setMetaType().

QString QSqlField::name() const

Returns the name of the field.

See also setName().

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

Returns true if this field differs from other; otherwise returns false.

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

Returns true if this field equals other in every respect, the value included; otherwise returns false.

int QSqlField::precision() const

Returns the precision of the field, or a negative number if the database does not tell.

See also setPrecision().

RequiredStatus QSqlField::requiredStatus() const

Returns whether the field must have a value when a row is inserted.

See also setRequiredStatus().

void QSqlField::setAutoValue(bool autoVal)

Marks the field as one that the database gives its value if autoVal is true.

See also isAutoValue().

void QSqlField::setDefaultValue(const QVariant &value)

Sets the default value of the field to value.

See also defaultValue().

void QSqlField::setGenerated(bool gen)

Sets whether the field takes part in generated SQL statements to gen.

See also isGenerated().

void QSqlField::setLength(int fieldLength)

Sets the length of the field to fieldLength: the number of characters of a string, for example.

See also length().

void QSqlField::setMetaType(QMetaType type)

Sets the type of the field to type. A null value takes the new type; another value stays as it is.

See also metaType().

void QSqlField::setName(const QString &name)

Sets the name of the field to name.

See also name().

void QSqlField::setPrecision(int precision)

Sets the precision of the field to precision: the number of digits after the decimal point of a number.

See also precision().

void QSqlField::setReadOnly(bool readOnly)

Makes the field read-only if readOnly is true, and writable otherwise. The value of a read-only field cannot be changed.

See also isReadOnly().

void QSqlField::setRequired(bool required)

Sets the required status of the field to Required if required is true, and to Optional otherwise.

See also setRequiredStatus().

void QSqlField::setRequiredStatus(RequiredStatus status)

Sets whether the field must have a value to status.

See also requiredStatus() and setRequired().

void QSqlField::setTableName(const QString &tableName)

Sets the name of the table that the field belongs to, to tableName.

See also tableName().

void QSqlField::setValue(const QVariant &value)

Sets the value of the field to value. Nothing happens if the field is read-only.

See also value(), isReadOnly() and clear().

void QSqlField::swap(QSqlField &other)

Swaps this field with other.

QString QSqlField::tableName() const

Returns the name of the table that the field belongs to, which may be empty.

See also setTableName().

QVariant QSqlField::value() const

Returns the value of the field. Use isNull() to tell a null value.

See also setValue().