<Source>.SeekFirst (Function)

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Generic search/Exact-match search
Performing a search on a composite key
Search on an array item
Search and filter
Locks

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<Source>.SeekFirst (Function)

In french: <Source>.RecherchePremier

Not available with this kind of connection

Positions on the first file record whose value for a specific item is greater than or equal to a sought value. The record is not read.

The number of the current record is modified only when it is returned by <Source>.RecNum. For the functions that handle the current record number (<Source>.Delete, <Source>.Read, <Source>.Modify, etc.), the value of this number is not updated: you must use <Source>.RecNum.
Example not to do:

// Supprime un enregistrement ne correspondant pas à celui voulu
Client.RecherchePremier(IDClient, 25)
Client.Supprime()

but:

// Suppression de l'enregistrement recherché
Client.RecherchePremier(IDClient, 25)
Client.Supprime(Client.NumEnr())

Caution: The record loaded in memory is not modified. The HFSQL variables (Customer.Name for example, which means the Name item of Customer file) are not updated.

In most cases, <Source>.SeekFirst sets the position in the data file to loop through the records that match a condition.

Several cases may occur after the call to <Source>.SeekFirst:

a record corresponding to the condition was found, locked (if necessary) and loaded in memory: <Source>.Found returns True.
the data file is empty or there is no record corresponding to the condition: <Source>.Out returns True.
the function tries to lock a record that is already locked in read-only: HErrorLock returns True and <Source>.Out returns True.

Remark: the search can be canceled by <Source>.CancelSeek.

Example

// Recherche du premier enregistrement pour lequel 
// le nom du Client est Dupond
Client.RecherchePremier(Nom, "Dupond")

// L'enregistrement n'est pas lu.
// Recherche tous les clients ayant un certain nom et prénom. 
// La recherche se fait selon une clé composée. 
bufValRech is Buffer = Client.ConstruitValClé(Nom_Prénom, sNom, sPrénom)
Client.RecherchePremier(Nom_Prénom, bufValRech, hLockWrite)
WHILE Client.Trouve() = True
	Client.Supprime(Client.NumEnr())
	Client.Suivant(Nom_Prénom, hLockWrite)
END

Syntax

<Result> = <Source>.SeekFirst(<Key item> , <Sought value> [, <Options>])

<Result>: Boolean

True if the position was set on the record (corresponds to the value of <Source>.Found).
False if a problem occurs. This problem can be caused by:
a positioning problem (empty data file, etc.): <Source>.Found returns False and HError returns 0.
an error: HError returns an integer other than 0. HErrorInfo returns more details.

<Source>: Type corresponding to the specified source

Name of the HFSQL data file used.

<Key item>: Character string

Name of key item on which the search will be performed.

<Sought value>: Type corresponding to the value

Value of the sought item.

<Options>: Optional constant (or combination of constants)

Configures:
the lock mode applied to the sought record
the type of search performed.
hGeneric Generic search (see the Notes)
An exact-match search is performed by default (constant not specified).
hKeepFilter The filter set by <Source>.Filter will be taken into account, even if the search key is not optimized for the filter. Reminder: <Source>.Filter returns the search key optimized for the filter.
Caution: in this case, performance problems may occur on large files.
This variable cannot be used.
By default, the iteration performed after <Source>.SeekFirst ignores the filter.
hLimitParsing The iteration will stop when the last searched value is found. The current record will correspond to this last record found.
<Source>.Found will return False and <Source>.Out will return True.
This constant is used to optimize the search speed in Client/Server mode.
hLockNo No lock: the record can be read or modified by another application during the reading.
hLockReadWrite Lock in read/write mode: the record currently read cannot be read or modified by another application.
Lock in write-only. Operating mode equivalent to the hLockWrite constant.
hLockWrite Lock in write mode: the record currently read can be read by another application but it cannot be modified by another application.
Access by JDBC: This parameter is ignored.
The lock options will have no effect if the locks are not supported by the OLE DB provider or by the Native Connector.
The lock mode specified by <Source>.SeekFirst will remain effective during the calls to <Source>.Previous and <Source>.Next.
To change the lock mode, use:
<Source>.SeekFirst or <Source>.SeekLast,
<Source>.First or <Source>.Last.

Remarks

Generic search/Exact-match search

Generic search (mainly on the Character String items): Finds all the records starting with the specified value.
For example: When a generic search is performed on "Smith" (for the NAME item), all records whose Name item starts with "Smith" will match the search. Therefore, the record containing "Smither" will correspond to the search (HFound returns True).
Exact-match search: Finds all the records that exactly correspond to the specified value.
For example: When an exact-match search is performed on "Smith" (for the NAME item), HFound returns True for the records whose item exactly matches "Smith".
Examples of searches performed on CUSTOMER file sorted by name:


Search value	Options	<Source>.SeekFirst sets the position on the record	<Source>.Found returns	<Source>.Out returns	Explanations
Durand		1	True	False	Durand exists. The end of data file was not reached yet.
Dupuis		1	False	False	Dupuis does not exist. Positioning on the first greater value (Durand). The end of data file was not reached yet.
Moor	hGeneric	8	True	False	Moor does not exist but the search is a generic search and Moore is found (among others). The end of data file was not reached yet.
Moor		The record was not found (no move)	False	False	Moor does not exist. The end of data file was not reached yet.
Norbert		The record was not found (no move)	False	True	Norbert does not exist. Position on the first greater value (this value does not exist): The end of data file has been reached.

Performing a search on a composite key

Several methods can be used to perform a search on a composite key:

Using a list of values,
Using the <Source>.BuildKeyValue function.

Using a list of values

The following syntax is used to perform a search on a composite key:

HSeekFirst(<File name>, <Name of composite key>, ...
[<Search value of first element of composite key>,
<Search value of first element of composite key>, ...])

Example:

// Recherche de l'enregistrement
Client.RecherchePremier(Nom_Prénom, ["Moulin","Françoise"])

To perform generic searches on a composite key, all the components of composite key must be Text components. Otherwise, an exact-match search is performed.

Search on an array item

The search is performed on the first array element (element with index 1). To perform a search on the other array elements, use the filters or queries.

Search and filter

If a filter is enabled (<Source>.Filter), the search takes the filter into account.

If a filter is enabled, the filter is ignored by the search.

Locks

The locks apply only when a record was found.

By default (no lock mode specified in <Options>), the record is not locked.

If a lock is requested (hLockWrite or hLockReadWrite constant), the record will be read only if this record is not already locked.

Reminder: A locked record can be unlocked by <Source>.UnlockRecNum.

The lock options will have no effect if the locks are not supported by the OLE DB provider or by the Native Connector.

Component: wd300hf.dll