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The SQL commands used for BULK table processing are:
BULK SELECT
BULK FETCH
BULK INSERT
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BULK SELECT | |
The BULK SELECT command is useful when the maximum number of
rows in the query result is known at programming time and when the
query result is not too large.
For example, this command might be used in
an application that retrieves a query result containing
a row for each month of the year. The syntax of the BULK SELECT command is:
BULK SELECT SelectList
INTO ArrayName [,StartIndex [,NumberOfRows]]
FROM TableNames
WHERE SearchCondition1
GROUP BY ColumnName
HAVING SearchCondition2
ORDER BY ColumnID
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Remember, the WHERE, GROUP BY, HAVING, and ORDER BY clauses are
optional. Note that the order of the select list items must match
the order of the corresponding host variables in the array. In the following example, parts are counted at one of three frequencies or
cycles: 30, 60, or 90 days. The host variable array needs to contain
only three records, since the query result will never exceed three rows.
EXEC SQL BEGIN DECLARE SECTION;
struct {
short int CountCycle;
int PartCount;
} PartsPerCycle[3];
EXEC SQL END DECLARE SECTION;
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EXEC SQL BULK SELECT CountCycle, COUNT(PartNumber)
INTO :PartsPerCycle
FROM PurchDB.Inventory;
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The query result is a three-row table that describes how many
parts are counted per count cycle. Multiple query results can be retrieved into the same
host variable array by using StartIndex and
NumberOfRows values and executing a BULK SELECT
command multiple times:
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EXEC SQL BEGIN DECLARE SECTION;
struct {
short int CountCycle;
int PartCount;
} PartsPerCycle[15];
short int StartIndex;
short int NumberOfRows;
char LowBinNumber[16];
char HighBinNumber[16];
EXEC SQL END DECLARE SECTION;
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int DisplayRows()
{
int i;
for (i = 0; i < StartIndex; i++) {
printf("CountCycle: %d\n", PartsPerCycle[i].CountCycle);
printf("PartCount: %d\n", PartsPerCycle[i].PartCount);
} /* end for */
} /* end of procedure DisplayRows */
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main()
{
#define TRUE 1
#define FALSE 0
typedef int boolean;
int StartIndex;
int NumberOfRows;
boolean LessThanFive;
/* Initialize variables. */
StartIndex = 0;
NumberOfRows = 3;
LessThanFive = TRUE;
do {
The user is prompted for a range of bin numbers or a 0. If bin numbers are entered, they are used in a BETWEEN predicate in the BULK SELECT command. This WHILE loop can be
executed as many as five times, at which time the array would be filled.
printf("\n Enter a low bin number or 0 to STOP > ");
scanf("%d",LowBinNumber);
if (LowBinNumber != 0) {
printf("\n Enter a high bin number > ");
scanf("%d\n",HighBinNumber);
EXEC SQL BULK SELECT CountCycle, COUNT(PartNumber)
INTO :PartsPerCycle,
:StartIndex,
:NumberOfRows
FROM PurchDB.Inventory
WHERE BinNumber
BETWEEN :LowBinNumber AND :HighBinNumber;
StartIndex = StartIndex + 3;
if (StartIndex == 15) LessThanFive = FALSE;
} /* if LowBinNumber */
else
LessThanFive = FALSE;
} while (LessThanFive == TRUE);
The final StartIndex value is used to display the final contents of the host variable array.
if (StartIndex > 0) {
DisplayRows();
}
}
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The following example illustrates the use of sqlca.sqlerrd[2] to display
rows stored in the host variable array. It also checks
sqlca.sqlcode in conjunction with sqlca.sqlerrd[2], to determine
whether or not the BULK SELECT executed without error and whether there
may be additional qualified rows for which there was not room in the
array. In each case, an appropriate message is displayed.
int DisplayRows()
{
int i;
for (i = 0; i < sqlca.sqlerrd[2]; i++) {
printf("OrderNumber: %s\n", OrdersArray[i].OrderNumber);
printf("VendorNumber: %s\n", OrdersArray[i].VendorNumber);
}
} (* end of procedure DisplayRows *)
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The variable MaximumRows is set to the number of records in the host variable array.
Main()
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MaximumRows = 25;
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EXEC SQL BULK SELECT OrderNumber, VendorNumber
INTO :OrdersArray
FROM PurchDB.Orders;
switch (sqlca.sqlcode) {
case 0: if (sqlca.sqlerrd[2] == MaximumRows) {
printf("\n There may be additional rows ");
printf("\n that cannot be displayed.");
}
DisplayRows();
break;
case 100: printf("\n No rows were found!");
break;
default: if (sqlca.sqlerrd[2] > 0) {
printf("\n The following rows were retrieved ");
printf("\n before an error occurred:");
}
DisplayRows();
SQLStatusCheck();
break;
} /* End switch */
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}
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BULK FETCH | |
The BULK FETCH command is useful for reporting applications that
operate on large query results or query results whose maximum
size is unknown at programming time. The syntax of the BULK FETCH command is:
BULK FETCH CursorName
INTO ArrayName [,StartIndex [,NumberOfRows]]
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You use this command in conjunction with the following cursor
commands: DECLARE CURSOR: defines a cursor and associates with it a
query. The cursor declaration should not contain a FOR UPDATE clause
because the BULK FETCH command is designed to be
used for active set retrieval only. The order of the select
list items in the embedded SELECT command must match the order
of the corresponding host variables in the host variable array. BULK FETCH: delivers rows into the host variable
array and advances the cursor to the last row delivered.
If a single execution of this command does not retrieve
the entire active set, you re-execute it to retrieve subsequent
rows in the active set. CLOSE: releases ALLBASE/SQL internal buffers used to handle cursor
operations.
To retrieve all the rows in an active set larger than the
host variable array, you can test for a value of 100 in
sqlca.sqlcode to determine when you have fetched the last
row in the active set:
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int DisplayRows()
{
int i;
for (i = 0; i < sqlca.sqlerrd[2]; i++) {
The values in each row returned by the BULK FETCH command are displayed here.
}
if (sqlca.sqlcode != 0) {
printf("\n Do you want to see additional rows? (yes/no) > ");
scanf("%s", Response);
if ((Response[0] == 'N') || (Response[0] == 'n')) {
DoFetch = FALSE;
}
} (* end of DisplayRows procedure *)
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main()
{
EXEC SQL BEGIN DECLARE SECTION;
struct {
char PartNumber[17];
char VendorName[31];
short int DeliveryDays;
sqlind DeliveryDaysInd;
} SupplierBuffer[20];
EXEC SQL END DECLARE SECTION;
typedef int boolean;
boolean DoFetch;
char Response[2];
#define TRUE 1
#define FALSE 0
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EXEC SQL DECLARE SupplierInfo
CURSOR FOR
SELECT PartNumber,
VendorName,
DeliveryDays
FROM PurchDB.Vendors,
PurchDB.SupplyPrice
WHERE PurchDB.Vendors.VendorNumber =
PurchDB.SupplyPrice.VendorNumber
ORDER BY PartNumber;
EXEC SQL OPEN SupplierInfo;
DoFetch = TRUE;
do {
EXEC SQL BULK FETCH SupplierInfo
INTO :SupplierBuffer;
switch (sqlca.sqlcode) {
case 0: DisplayRows();
break;
case 100: printf("\n No rows were found!");
DoFetch = FALSE;
break;
default: DisplayRows();
SQLStatusCheck();
DoFetch = FALSE;
break;
} /* End switch */
} while (DoFetch != TRUE);
EXEC SQL CLOSE SupplierInfo;
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After the BULK FETCH command is executed, the last row
ALLBASE/SQL put into the host variable array is the current row.
If the BULK FETCH command is re-executed, the first row
in the next set of rows fetched is the row following the current
row, and the last row fetched becomes the current row.
When the last row in the active set has been fetched, ALLBASE/SQL
sets sqlca.sqlcode to 100 the next time the BULK FETCH
command is executed. BULK INSERT | |
The BULK INSERT command is useful for multiple-row insert operations. The form of the BULK INSERT command is:
BULK INSERT INTO TableName
(ColumnNames)
VALUES (ArrayName [,StartIndex [,NumberOfRows]]
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As in the case of the simple INSERT command,
you can omit ColumnNames when you provide values for all columns
in the target table. ALLBASE/SQL attempts to assign a null value to any
unnamed column. In the following example, a user is prompted
for multiple rows. When the host
variable array is full and/or when the user is finished specifying values,
the BULK INSERT command is executed:
EXEC SQL BEGIN DECLARE SECTION;
struct {
char PartNumber[17];
char PartName[31];
sqlind PartNameInd;
double SalesPrice;
sqlind SalesPriceInd;
} NewParts[20];
short int StartIndex;
short int NumberOfRows;
EXEC SQL END DECLARE SECTION;
typedef int boolean;
boolean DoneEntry;
char Response[2];
#define TRUE 1
#define FALSE 0
StartIndex = 0;
NumberOfRows = 0;
DoneEntry = FALSE;
do {
PartEntry();
} while (DoneEntry != TRUE);
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int BulkInsert()
{
EXEC SQL BULK INSERT INTO PurchDB.Parts
(PartNumber,
PartName,
SalesPrice)
VALUES (:NewParts,
:StartIndex,
:NumberOfRows);
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} /* End of function BulkInsert */
int PartEntry()
{
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You are prompted for three column values, and the values are assigned to the appropriate
record in the host variable array; then the array row counter (NumberOfRows) is incremented
and you are asked whether you want to specify another line item.
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NumberOfRows = NumberOfRows + 1;
printf("\n Do you want to specify another line item (Y/N)? > ");
scanf("%s",Response);
if ((Response[0] == 'N') || (Response[0] == 'n')) {
DoneEntry = TRUE;
BulkInsert();
}
else {
if (NumberOfRows == 20) {
BulkInsert();
NumberOfRows = 0;
}
} /* End else */
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} /* End of PartEntry Function */
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