Oracle CQL Queries, Views, and Joins 18-17
The binding element must contain one or more params elements. Each params element must have a unique id and must contain a comma separated list of parameter
values equal in number to the number of placeholder characters :n in the corresponding query.
The order of the parameter values corresponds to placeholder characters :n in the parameterized query, such that :1 corresponds to the first parameter value, :2
corresponds to the second parameter value, and so on. You may use placeholder characters :n in any order. That is, :1 corresponds to the first parameter value
whether it precedes or follows :2 in a query. A placeholder number can be used only once in a query.
For more information, see:
■
Section 18.2.11.4, Lexical Conventions for Parameter Values
■
Section 18.2.11.5, Parameterized Queries at Runtime
18.2.11.3 Run-Time Query Naming
When a binding instantiates a parameterized query, Oracle CEP creates a new query at run time with the name queryId_paramId. For example, in
Example 18–11 , the
run-time name of the first query instantiated by the MarketRule binding is MarketRule_nasORCL.
To avoid run-time naming conflicts, be sure query ID and parameter ID combinations are unique.
18.2.11.4 Lexical Conventions for Parameter Values
Each params element must have a unique id and must contain a comma separated list of parameter values equal in number to the number of placeholder characters :n
in the corresponding query.
In an Oracle CQL query, a placeholder within single or double quotes is a String literal. The following query is not a parameterized query:
SELECT :1 as symbol, price FROM StockTick [RANGE 5 SECONDS] Oracle CEP parses this query as assigning the String literal :1 to alias symbol. To
make this query into a parameterized query, use: SELECT :1 as symbol, price FROM StockTick [RANGE :2 SECONDS]
And define a params element like this: params id=p1ORCL, 5params
Table 18–2 Parameterized Query Parameter Value Lexical Conventions
Convention Example
Replacement Value
Primitive type literals params id=p1NASDAQ, 200.0params
:1 = NASDAQ :2 = 200.0
Oracle CQL fragments params id=p1count, avgvalparams
:1 = count :2 = avgval
Quotes params id=p1’alert’, Seattle, WA,
’fun’ || house, one two 3params :1 = ’alert’
:2 = Seattle, WA :3 = ’fun’ || house
:4 = one two 3
18-18 Oracle Complex Event Processing CQL Language Reference
Because the parameter value ORCL does not contain a comma, the quotes are not required. You could specify a params element like this:
params id=p1ORCL, 5params However, if the parameter value does contain a comma, then you must use quotes
around the parameter value. Consider this parameterized query: SELECT :1 = cityAndState AS cityOfInterest FROM channel1 [RANGE :2 SECONDS]
Where cityAndState has values like Seattle, WA or Ottawa, ON. In this case, you must specify a params element like this:
params id=p1Seattle, WA, 5params params id=p1Ottawa, ON, 5params
Commas are allowed only in quoted parameter values that signify string values. Commas are not allowed as a separator character in unquoted parameter values. For
example:
Seattle, WA is valid, because the comma is part of the string. PARTITION BY fromRate,toRate ROWS 10 is invalid. Create the following two
parameters instead: PARTITION BY fromRate ROWS 10
PARTITION BY toRate ROWS 10
18.2.11.5 Parameterized Queries at Runtime
Each params element effectively causes a new Oracle CQL query to execute with the new parameters. At rule execution time, Oracle CQL substitutes parameter values for
placeholder characters, from left to right. Example 18–11
is effectively equivalent to the queries that
Example 18–12 shows.
Example 18–12 Equivalent Queries at Runtime
SELECT symbol, AVGprice AS average, NASDAQ AS market FROM StockTick [RANGE 5 SECONDS]
WHERE symbol = ORCL
SELECT symbol, AVGprice AS average, NYSE AS market FROM StockTick [RANGE 5 SECONDS]
WHERE symbol = JPM
SELECT symbol, AVGprice AS average, NYSE AS market FROM StockTick [RANGE 5 SECONDS]
WHERE symbol = WFC
18.2.11.6 Replacing Parameters Programmatically
If you use the CQLProcessorMBean.replaceAllBoundParameters method to programmatically replace parameters in a parameterized query, any existing
parameters not replaced by the method are automatically removed from the query.
18.3 Views
Queries are the principle means of extracting information from data streams and relations. A view represents an alternative selection on a stream or relation that you
can use to create subqueries.
Oracle CQL Queries, Views, and Joins 18-19
A view is only accessible by the queries that reside in the same processor and cannot be exposed beyond that boundary.
You can specify any query type in the definition of your view. For more information, see
Section 18.2, Queries .
For complete details on the view statement, see View
on page 20-25. In
Example 18–13 , query BBAQuery selects from view MAXBIDMINASK which in turn
selects from other views such as BIDMAX which in turn selects from other views. Finally, views such as lastEvents select from an actual event source:
filteredStream. Each such view represents a separate derived stream drawn from one or more base streams.
Example 18–13 Using Views Instead of Subqueries
view id=lastEvents schema=cusip bid srcId bidQty ask askQty seq[CDATA[ select cusip, bid, srcId, bidQty, ask, askQty, seq
from filteredStream[partition by srcId, cusip rows 1] ]]view
view id=bidask schema=cusip bid ask[CDATA[ select cusip, maxbid, minask
from lastEvents group by cusip
]]view view id=bid schema=cusip bid seq[CDATA[
select ba.cusip as cusip, ba.bid as bid, e.seq from bidask as ba, lastEvents as e
WHERE e.cusip = ba.cusip AND e.bid = ba.bid ]]view
view id=bid1 schema=cusip maxseq[CDATA[ select b.cusip, maxseq as maxseq
from bid as b group by b.cusip
]]view view id=BIDMAX schema=cusip seq srcId bid bidQty[CDATA[
select e.cusip, e.seq, e.srcId, e.bid, e.bidQty from bid1 as b, lastEvents as e
where e.seq = b.maxseq ]]view
view id=ask schema=cusip ask seq[CDATA[ select ba.cusip as cusip, ba.ask as ask, e.seq
from bidask as ba, lastEvents as e WHERE e.cusip = ba.cusip AND e.ask = ba.ask
]]view view id=ask1 schema=cusip maxseq[CDATA[
select a.cusip, maxseq as maxseq from ask as a
group by a.cusip ]]view
view id=ASKMIN schema=cusip seq srcId ask askQty[CDATA[ select e.cusip, e.seq, e.srcId, e.ask, e.askQty
from ask1 as a, lastEvents as e where e.seq = a.maxseq
]]view view id=MAXBIDMINASK schema=cusip bidseq bidSrcId bid askseq askSrcId ask bidQty
askQty[CDATA[ select bid.cusip, bid.seq, bid.srcId as bidSrcId, bid.bid, ask.seq, ask.srcId as
askSrcId, ask.ask, bid.bidQty, ask.askQty from BIDMAX as bid, ASKMIN as ask
where bid.cusip = ask.cusip ]]view
query id=BBAQuery[CDATA[ ISTREAMselect bba.cusip, bba.bidseq, bba.bidSrcId, bba.bid, bba.askseq, bba.askSrcId,
bba.ask, bba.bidQty, bba.askQty, BBAStrategy as intermediateStrategy, p.seq as
