SQLFirst (Function)

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Loading the query in memory
Partial Fetch
Various

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SQLFirst (Function)

In french: SQLPremier

Positions on the first row of the query result. This row becomes the current row.

If controls or variables are associated with the columns of query result (SQLAssociate), the values found in the current row are automatically assigned to these elements.

In most cases, SQLFirst is used in a read loop with SQLNext.

Caution: This function must be used during a SQLFirst/SQLCol browse of query result. See Types of SQL browse for more details.

Example

See additional examples

// Initialize the scrollbar parameters at the end of query
ResSQL = SQLExec("SELECT CUSTLASTNAME, FIRSTNAME, ADDR1, ADDR2, CITY, ZIP FROM CUSTOMER", ...
"QRY1")
IF ResSQL = True THEN
// Displays the first row
SQLFirst("QRY1")
// Initializes the upper bound of the scrollbar
SCROLL_SCROLL1..MaxValue = SQL.NbLine
// Positions the scrollbar at the beginning
SCROLL_SCROLL1 = 1
ELSE
// Processes the error
END
SQLClose("QRY1")

Syntax

SQLFirst([<Number of rows>, ] <Query name>)

<Number of rows>: Optional integer

Number of rows that will be loaded in memory every second. This number of rows will constitute a block for the partial Fetch.
Parameter required to perform a read by partial Fetch.

<Query name>: Character string (with or without quotes)

Query name:
created and run by SQLExec (with quotes),
run by SQLExecWDR (with or without quotes).

Remarks

Loading the query in memory

If SQLFirst is immediately called after SQLExec, the query result is loaded in memory. Two methods are available:

Entirely load the query in memory if <Number of Lines> is not specified. The number of records corresponding to the query result is automatically calculated. The SQL.NbLine variable is updated.
Partially load the query in memory (also called partial fetch) if <Number of rows> is specified.
Only the first block of rows is loaded in memory. The following blocks are automatically loaded in background task (mechanism of partial fetch). The SQL.Retrieving variable (updated by SQLInfo) is used to find out whether the result was entirely retrieved.
Remark: Depending on the process performed, the partial fetch is used to reduce the network bandwidth.

Partial Fetch

If you are using the Partial Fetch to retrieve the query result (see the example for this function):

If SQLClose is called while the retrieval is not completed, the retrieval is stopped and the query is closed.
This method can be used with several queries at the same time.
The SQL.Retrieving variable (updated by SQLInfo) is used to find out whether the result was entirely retrieved.

Various

If the pointer is positioned outside the query result, the SQL.Out variable is set to True.
The SQL.Current variable contains the number of the current line.
SQLTable must not be used after SQLFirst. A fatal error is generated.

Component : wd250hf.dll