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Very often very when you are engaged with a great quantity of data, you've the need to restrict the view of these data to a little part, filtering with some criteria.TSearcher does
that! It helps you to filter a great amount of data, viewing only those especting such criteria applyed to some key-fields.TSearcher is a component which gives its best performances in client/server applications, where
limit the amount of data to that ones which are really necessary is a must. For that reason i've not exploited the dataset filtering instructions, as these instructions, in particular cases, bring the whole data
cursor in your local memory and only here they apply the filter. Viceversa, TSearcher filters the data only at server level.
Tsearcher builds a SQL statement with some search criteria; the used SQL is based on
SQL97 standard and it has been proved with the main database engines like Paradox, Access, Interbase, MSSQL. It is possible to exploit different filter criteria, thanks to various logical operators like the exactly
equal sign, the between sign and also it is possible to check if a field has a value or is null. For string field you can set the 'start with' operator, the it 'Contains' operator the non case sensitive search even if
not supported by the used database engine. Another caracteristics you have, is the possibility to filter with a date or time on a
dateTime field, or to consider a string field as a boolean one, giving to a symbol the true
value and to another one the false value. TSearcher is given with 3 different versions, depending on the used database
engine: the BDE version (which uses the TQuery); the DAO version (which uses the TDAOQuery of the DAO Database Collection of Erik Salaj); the ADO version for Delphi 5 (which uses the TADOQuery). |
