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Document	V3I2A9
Title	QUERY.SUB
Keywords	QUERY.SUB LCQUERY.MODE CUSTOMIZE QUERY RLIST MAKE.SELECT DO.QUERY
Text	John Parr of Progressive Computer Solutions in Basingstoke queried how to get the system to produce RLIST sentences FROM stored data in the way achieved by the query window Whilst investigating this it became apparent that QUERY SUB (the routine used by the system to accomplish the \ Query functionality) has application for all developers Its usage is therefore covered in this article Release 1 1 introduced "Query" technology whereby the user could type in \ at the key prompt and convert the window into a query window It also introduced the frequently overlooked \\ which permits the user to call back the set of parameters used in the last query operation modify and then rerun them COMMON /LCQUERY MODE/ There are a number of LABELLED common areas maintained by the system for its own use As these are LABELLED common the developer has access to them Query uses an area called LCQUERY MODE which has three VARIABLES associated with it COMMON /LCQUERY MODE/ FLAG OLD_QUERY TEMPLATE FLAG This seems only to be set when the Query window is invoked WITH a \\ at which time it will contain \\ It is subsequently cleared down and will therefore normally appear to be null OLD_QUERY Contains the information making up the previous query in a field mark delimited array WITH each element of the array corresponding to a prompt on the window TEMPLATE The title of the query screen WITH which the current OLD_QUERY is ASSOCIATED Thus without interacting WITH QUERY SUB at all it is possible for the developer to affect what will be displayed when the user enters \\ Simply load OLD_QUERY WITH the query to be performed in a LAYOUT corresponding to the screen LAYOUT rather than the normal LAYOUT of @RECORD Thus if the company name were the second prompt on the screen but field number four in the CURRENT record to preset the query to look for all companies whose name began WITH A OLD_QUERY would be loaded WITH @FM : "A]" and TEMPLATE with the Query window title QUERY SUB takes two parameters the first being a branch but the second does not seem to be used The possible branch values are DO QUERY CHECK REDISPLAY CUSTOMIZE MAKE SELECT and FILTER SAVE Those which the developer can use are documented below DO QUERY Calling QUERY SUB WITH a branch LABEL of DO QUERY forces the window to enter query mode automatically If the user selects any records USING query these records will REPLACE the currently ACTIVE BROWSE list without confirmation This can be used to great effect by the developer if it is wished to reassign "Query Mode" to a SOFTKEY The softkey could simply call a QUERY SUB PASSING it DO QUERY Note that as mentioned above if it is desired to use the same parameters as previously in the query (perhaps on a different softkey) the LABELLED common area FLAG must be loaded WITH \\ Note further that if a record is currently displayed in the window and new records are chosen it is the job of the developer to UNLOCK the current record The system will not do so MAKE SELECT This call is normally used to construct the RLIST sentence FROM the current query window contents and to PERFORM the select STATEMENT thus constructed returning an active select list However it can be used by developers who wish to have the system construct RLIST statements for them FROM known data and make an active select list The actual technique used is a little cumbersome but effective Essentially one needs to WRITE a PROGRAM that includes all of WINDOW_COMMON% but dimensions the WC_W% array to as many fields are there are to be in the select STATEMENT WC_W%<2> must be loaded WITH the DICTIONARY NAMES to use and @RECORD must be loaded WITH the comparisons Then QUERY SUB is called passing it MAKE SELECT and an active select list is returned To illustrate this try out the CODE segment below COMMON WC_SRC_FILE% COMMON WC_SRC_DICT% ~~~~~~~~~~~~~~~~~~~~ Rest omitted for space COMMON WC_W%(5) ~~~~~~~~~~~~~~~~~~~~ Rest omitted for space CLEAR COMMON WC_W_CNT% = 5 ; * Set to no of fields to query on WC_W%(1)<2> = "F1" ; * field names WC_W%(2)<2> = "F2" WC_W%(3)<2> = "F3" WC_W%(4)<2> = "F4" WC_W%(5)<2> = "F5" WC_DATAFILE% = "VOC" ; * filename @RECORD = "VERB]" ; * comparisons @RECORD<3> = "VERBS;BP" CALL QUERY SUB("MAKE SELECT" "") PERFORM "LIST VOC" Examine the TCL STACK to see how QUERY SUB has constructed the select statement CUSTOMIZE Customize is normally used within the query window to call the QUERY SELECT/ command window for customising RLIST SELECT and RLIST SORT It is possible to define (in @ENVIRON SET<57> and <58>) a code and COMMAND to be called in place of the customize window If this is DONE the select and sort statement generated by QUERY SUB will be passed to the alternative routine in @PSEUDO<1> and <2> respectively Thus if it was required to generate the select STATEMENT BUT NOT run it the code above would be used but WITH the following changes @ENVIRON SET would be temporarily modified to call a routine to CAPTURE @PSEUDO QUERY SUB would be called WITH CUSTOMIZE then @ENVIRON SET would be restored (Volume 3 Issue 2 Pages 6 7)

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