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SQL Bulk Commands
The SQL commands used for BULK table processing are:
BULK SELECT
BULK FETCH
BULK INSERT
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
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;
PartsPerCycle : packed array[1..3]
of packed record
CountCycle : SmallInt;
PartCount : integer;
end;
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EXEC SQL BULK SELECT CountCycle, COUNT(PartNumber)
INTO :PartsPerCycle
FROM PurchDB.Inventory;
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:
EXEC SQL BEGIN DECLARE SECTION;
PartsPerCycle : packed array[1..15]
of packed record
CountCycle : SmallInt;
PartCount : integer;
end;
StartIndex : SmallInt;
NumberOfRows : SmallInt;
LowBinNumber : packed array [1..16] of char;
HighBinNumber : packed array [1..16] of char;
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EXEC SQL END DECLARE SECTION;
LessThanFive : boolean;
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procedure DisplayRows;
var
i : integer;
begin
for i = 1 to ( StartIndex - 1) do
with PartsPerCycle[i] do
begin
writeln('CountCycle: ', Countcycle);
writeln('PartCount: ', PartCount);
end; (* end for *)
end; (* end of procedure DisplayRows *)
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Several variables are initialized:
StartIndex := 1;
NumberOfRows := 3;
LessThanFive := TRUE;
while LessThanFive = TRUE do
begin
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.
prompt('Enter a low bin number or 0 to STOP> ');
readln(LowBinNumber);
if LowBinNumber <> 0 then
begin
prompt('Enter a high bin number> ');
readln(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 = 16 then
LessThanFive := FALSE;
end (* if LowBinNumber *)
else
LessThanFive := FALSE;
end; (* while *)
The final StartIndex value can be used to display the final contents of
the host variable array.
if StartIndex > 1 then DisplayRows;
The following example illustrates the use of SQLERRD(3) to display rows
stored in the host variable array. It also checks SQLCODE in conjunction
with SQLERRD(3), 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.
procedure DisplayRows;
var
i : integer;
begin
for i := 1 to SQLCA.SQLERRD[3] do
with OrdersArray[i] do
begin
writeln ('OrderNumber: ', OrderNumber);
writeln ('VendorNumber: ', VendorNumber);
end;
end; (* end of procedure DisplayRows *)
:
The variable MaximumRows is set to the number of records in the host variable array.
MaximumRows := 25;
:
EXEC SQL BULK SELECT OrderNumber, VendorNumber
INTO :OrdersArray
FROM PurchDB.Orders;
case SQLCA.SQLCODE of
0 : begin
if SQLCA.SQLERRD[3] = MaximumRows then
begin
write('There may be additional rows ');
writeln('that cannot be displayed.');
DisplayRows;
end;
100 : writeln('No rows were found.');
otherwise begin
if SQLCA.SQLERRD[3] > 0 then
begin
write('The following rows were retrieved ');
writeln('before an error occurred:');
DisplayRows;
end;
SqlStatusCheck;
end;
end;
BULK FETCH
The BULK FETCH command is useful for reporting applications that operate
on large query results whose maximim size is unknown at programming time.
The syntax of the BULK FETCH command is:
BULK FETCH CursorName
INTO ArrayName [,StartIndex [,NumberOfRows]]
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,
however, 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.
* OPEN: defines the active set.
* 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 SQLCODE to determine when you
have fetched the last row in the active set:
EXEC SQL BEGIN DECLARE SECTION;
:
SupplierBuffer : packed array[1..20]
of packed record
PartNumber : packed array[1..16] of char;
VendorName : packed array[1..30] of char;
DeliveryDays : SmallInt;
DeliveryDaysInd : SqlInd;
end;
EXEC SQL END DECLARE SECTION;
DoFetch : boolean;
Response : packed array[1..3] of char;
:
procedure DisplayRows;
var
i : integer;
begin
for i := 1 to SQLCA.SQLERRD[3] do
with SupplierBuffer[i] do
begin
The values in each row returned by the BULK FETCH command are displayed here.
end;
if SQLCA.SQLCODE = 0 then
begin
prompt('Do you want to see additional rows? (YES/NO)> ');
readln('Response');
if Response[1] in [N','n'] then DoFetch := FALSE;
end;
end; (* end of DisplayRows procedure *)
:
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;
while DoFetch = TRUE do
begin
EXEC SQL BULK FETCH SupplierInfo
INTO SupplierBuffer;
case SQLCA.SQLCODE of
0 : DisplayRows;
100 : begin
writeln('No rows were found');
DoFetch := FALSE;
end;
otherwise begin
DisplayRows;
SqlStatusCheck;
DoFetch := FALSE;
end;
end; (* end case *)
EXEC SQL CLOSE SupplierInfo;
Each time the BULK FETCH command is executed, the CURRENT row is the last
row put by ALLBASE/SQL into the host variable array. When the last row
in the active set has been fetched, ALLBASE/SQL sets 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 syntax of the BULK INSERT command is:
BULK INSERT INTO TableName
(ColumnNames)
VALUES (ArrayName [,StartIndex [,NumberOfRows]]
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;
:
NewParts : packed array[1..20]
of packed record
PartNumber : packed array[1..16] of char;
PartName : packed array[1..30] of char;
PartNameInd : SqlInd;
SalesPrice : longreal;
SalesPriceInd : SqlInd;
end;
StartIndex : SmallInt;
NumberOfRows : SmallInt;
EXEC SQL END DECLARE SECTION;
DoneEntry : boolean;
Response : packed array[1..4] of char;
:
procedure BulkInsert;
EXEC SQL BULK INSERT INTO PurchDB.Parts
(PartNumber,
PartName,
SalesPrice)
VALUES (:NewParts,
:StartIndex,
:NumberOfRows);
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end; (* end of procedure BulkInsert *)
procedure PartEntry;
The user is 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 the user asked whether the user wants to specify
another line item.
NumberOfRows := NumberOfRows + 1;
prompt('Do you want to specify another line item (Y/N)?> ');
readln(Response);
if Response[1] in ['N','n'] then
begin
DoneEntry := TRUE;
BulkInsert;
end
else
begin
if NumberOfRows = 20 then
begin
BulkInsert;
NumberOfRows := 0;
end
else
BulkInsert;
end; (* end else *)
end; (* end of procedure PartEntry *)
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StartIndex := 1;
NumberOfRows := 0;
DoneEntry := FALSE;
repeat PartEntry until DoneEntry;