Class TDbQuery

class TDbQuery;

Description

A wrapper for an SQL string combined with a text comparison mode.

An instance of the class is used as a parameter to RDbView::Prepare(RDbDatabase &,const TDbQuery &,TAccess), RDbRowSet::FindL(TDirection,TDbQuery) and RDbRowConstraint::Open(const RDbRowSet &,TDbQuery).

The evaluation of SQL queries or constraints depends on how Text columns are compared so every SQL string is accompanied by a member of the TDbTextComparison enumeration to indicate how comparison is done.

If the SQL string contains a LIKE clause with * (asterisks) wildcard then the characters between them must be no longer than length 255. If only one * exists then the length is taken from the start and to the end of the clause. However, if the clause contains a ? (question mark) wildcard within it then the characters between must be no longer than length 253.

Members

Defined in TDbQuery:

• Comparison()constReturns the text comparison mode for the query object.
• Query()constReturns the SQL string in the query object.
• TDbQuery(const TDesC &,TDbTextComparison)Constructs a query object from an SQL string and a text comparison mode.

See also:

• TDbTextComparisonRepresents different ways of comparing Text and LongText columns.
• RDbView::Prepare(RDbDatabase &,const TDbQuery &,TAccess)Prepares the view object for evaluating an SQL select-statement.
• RDbRowSet::FindL(TDirection,TDbQuery)Searches through a rowset for a row which fulfils an SQL search-condition. The s...
• RDbRowConstraint::Open(const RDbRowSet &,TDbQuery)Compiles the specified SQL search-condition for matching against rows in the spe...

inline TDbQuery(const TDesC &aQuery, TDbTextComparison aComparison=EDbCompareNormal);

Description

Constructs a query object from an SQL string and a text comparison mode.

Note that no copy is made of the descriptor passed; it is stored by reference in the query object.

Parameters

const TDesC16 &aQuery The SQL string as a descriptor. TDbTextComparison aComparison The type of text comparison to use in evaluation of the SQL. If not supplied, normal comparison is used.

inline const TDesC& Query() const;

Description

Returns the SQL string in the query object.

Return value

const TDesC16 & A descriptor containing the SQL string.

inline TDbTextComparison Comparison() const;

Description

Returns the text comparison mode for the query object.

Return value

TDbTextComparison The text comparison mode.