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- Browse item
- Browsing queries
- Locks
- Memos
- Password
- Native XML Connector
- Miscellaneous
<Source>.ReadFirst (Function) In french: <Source>.LitPremier
Not available with this kind of connection
Positions on the first file record according to a browse item. The record is read and the HFSQL variables (e.g. Customer.Name, i.e. the field Name field of the data file Clientdata file) are updated. Values in the browse item are read in ascending order (for more details, see the the remarks). In most cases, <Source>.ReadFirst is used to set the position in the data file in order to perform a read loop with <Source>.ReadNext. Several cases may occur after the call to <Source>.ReadFirst: - the data file is empty or no record exists corresponding to the filter (defined by <Source>.Filter): no read is performed and function <Source>.Out returns True.
- the function attempts to read a record already blocked in playback: no playback is performed, function HErrorLock returns True and function <Source>.Out returns True.
The management of locks is not available.
JDBC access: lock management is not supported for databases that are accessed through JDBC.
This function can be used with the data files, HFSQL views or queries.
Customer.ReadFirst(Name)
WHILE Customer.Out() = False
Customer.ReadNext(Name)
END
Syntax
<Result> = <Source>.ReadFirst([<Browse item> [, <Options>]])
<Result>: Boolean Corresponds to: - False if an error occurs. In this case, HError returns an integer other than 0. HErrorInfo returns more details about the error. The record is not read.
- the value of <Source>.Found in the other cases (the record can be read, even if <Result> returns False).
<Source>: Type corresponding to the specified source Name of data file, HFSQL view or query used. <Browse item>: Optional character string Name of the item used to browse the data file or view (this parameter is not taken into account for queries). If this name is not specified, <Source>.ReadFirst will use:- In the case of a data file the last browse item used on this file by the last HFSQL management function (function beginning with the letter H). If this item does not exist, the best browse item is automatically used.
- In the case of a query ORDER BY of the query if it exists, otherwise according to the last field used.
- In the case of a view: the sort item of the view (if there is one), otherwise the last item used.
<Options>: Optional constant Used to configure:- the lock set on the record read by <Source>.ReadFirst
- whether the filter that was defined must be taken into account.
| | hForwardOnly | | hKeepFilter | The filter set by <Source>.Filter will be taken into account, even if the search key is not optimized for the filter. Reminder function <Source>.Filter returns the optimized route key for the filter. Caution: in this case, on large data files, performance problems may occur..
| hLockNo | No blocking: the recording can be played back or modified by another application during playback..
| hLockReadWrite | Read/write lock: the record being read cannot be read or modified by another application.
| hLockWrite | Write lock: the record currently read can be read by another application but it cannot be modified by another application.
| hNoRefresh | |
Remarks Browse item If the browse item is a key, <Source>.ReadFirst reads the record with the lowest key value. The sort order taken into account is the one specified in the analysis for this key. If duplicates are found, <Source>.ReadFirst reads the first "duplicate" record according to the sequence of record numbers. If the browse item is not a key, <Source>.ReadFirst reads the first active record. When browsing the data file, the records will be sorted according to their record number. In this case, the selected browse item will appear in red in the code editor and a warning will be displayed in the "Code" pane. Memos The memos associated with the record can be automatically read (or not) when reading the record. <Source>.SetMemo is used to customize this automatic read operation. If the memos are supported, the associated text memos are read when the record is read. The binary memos are read only when they are explicitly used ( <Source>.ExtractMemo). Password If <Source>.ReadFirst is the first function that handles the specified data file, the password is checked when the opening data file. If the password is incorrect, HErrorPassword returns True and <Source>.Out returns True. Miscellaneous - <Source>.RecNum returns the current record number.
- <Source>.ChangeKey changes the search key while keeping the position on the current record.
- To optimize the time taken for the first few runs of a data file, use function <Source>.Optimize.
- This function replaces HReadFirstLock and HReadFirstNoLock, which were kept for compatibility with WINDEV 5.5.
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