QSqlField

PyQt5.QtSql.QSqlField

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

#     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. For example:

#     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.

Enums

RequiredStatus

Specifies whether the field is required or optional.

See also

requiredStatus().

Member	Value	Description
Optional	0	The fields doesn’t have to be specified when inserting records.
Required	1	The field must be specified when inserting records.
Unknown	-1	The database driver couldn’t determine whether the field is required or optional.

Methods

__init__(QSqlField)

Constructs a copy of other.

---

__init__(fieldName: str = '', type: Type = Invalid)

Constructs an empty field called fieldName of variant type type.

See also

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

---

__init__(str, Type, str)

This is an overloaded function.

Constructs an empty field called fieldName of variant type type in table.

See also

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

---

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().

---

defaultValue() → Any

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

See also

setDefaultValue(), type(), requiredStatus(), length(), precision(), isGenerated().

---

__eq__(QSqlField) → bool

TODO

---

isAutoValue() → bool

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 record() or primaryIndex().

See also

setAutoValue().

---

isGenerated() → bool

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

See also

setGenerated(), type(), requiredStatus(), length(), precision(), defaultValue().

---

isNull() → bool

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

See also

value().

---

isReadOnly() → bool

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

See also

setReadOnly(), type(), requiredStatus(), length(), precision(), defaultValue(), isGenerated().

---

isValid() → bool

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

---

length() → int

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().

---

name() → str

Returns the name of the field.

See also

setName().

---

__ne__(QSqlField) → bool

TODO

---

precision() → int

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() → RequiredStatus

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().

---

setAutoValue(bool)

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

See also

isAutoValue().

---

setDefaultValue(Any)

Sets the default value used for this field to value.

See also

defaultValue(), value(), setType(), setRequiredStatus(), setLength(), setPrecision(), setGenerated(), setReadOnly().

---

setGenerated(bool)

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(), setType(), setRequiredStatus(), setLength(), setPrecision(), setDefaultValue(), setReadOnly().

---

setLength(int)

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().

---

setName(str)

Sets the name of the field to name.

See also

name().

---

setPrecision(int)

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

See also

precision(), setType(), setRequiredStatus(), setLength(), setDefaultValue(), setGenerated(), setReadOnly().

---

setReadOnly(bool)

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().

See also

isReadOnly().

---

setRequired(bool)

TODO

---

setRequiredStatus(RequiredStatus)

Sets the required status of this field to required.

See also

requiredStatus(), setType(), setLength(), setPrecision(), setDefaultValue(), setGenerated(), setReadOnly().

---

setSqlType(int)

TODO

---

setTableName(str)

Sets the tableName() of the field to table.

See also

tableName().

---

setType(Type)

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

See also

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

---

setValue(Any)

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().

---

tableName() → str

Returns the 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 record() of a forward-only query.

See also

setTableName().

---

type() → Type

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().

---

typeID() → int

Returns the type ID for the field.

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

---

value() → Any

See also

setValue().