While select statement

A while select statement is used to handle data. It's the most widely used form of the select statement. The while select statement loops over many records that meet specific criteria, and can run a statement on each record. The syntax of a while select statement resembles the syntax of a select statement, but the statement is preceded by while select instead of select.

  • Typically, when you use the while select statement for data manipulation, you use it in a transaction to ensure data integrity.

  • The results of the while select statement are returned in a table buffer variable.

  • If you use a field list in the select statement, only those fields are available in the table variable.

  • If you use aggregate functions, such as sum or count, the results are returned in the fields that you perform the sum or count over. You can count, average, or sum only integer and real fields.

  • The select statement itself is run only one time, immediately before the first iteration of the statements in the loop.

  • Any Boolean expressions that are added to the while select statement (for example, iCounter < 1) are tested only one time. This behavior differs from the behavior of the while statement in languages such as C++ and C#. For example, the following loop can have more than one iteration.

    int iCounter = 0;
    BankAccountTable xrecBAT;
    while select * from xrecBAT
        where iCounter < 1
        info(strFmt("%1 , %2", iCounter, xrecBAT.AccountID));

The following example prints the AccountNum and SalesGroup values of every customer in the CustTable table whose account number is within a specified range.

CustTable custTable;

while select custTable
    order by custTable.AccountNum
    where  custTable.AccountNum >= '4010' && custTable.AccountNum <= '4100'
    info(strFmt("%1 , %2", custTable.AccountNum, custTable.SalesGroup));