SAS Certification Handout #10: Adv. Prog. Ch. 5-8

Transcription

1 SAS Certification Handout #10: Adv. Prog. Ch. 5-8 /************ Ch. 5 ******************* /* First, make example data -- same as Handout #9 libname cert 'C:/jrstevens/Teaching/SAS_Cert/AdvNotes'; /* In SAS Studio, after creating SAS_Cert folder with username jrstevens: libname cert '/home/jrstevens/sas_cert'; data cert.sales10; format LastName $9. Sales dollar8.; input LastName $ EmplID Division $ Sales; cards; Smith 315 A Nelson 333 A Uribe 612 C Larson 331 B Larsen 216 B Rasmussen 217 A Knecht 861 B D'Angelou 772 A Larson 331 C ; /* CREATE TABLE -- three ways: (1) from query (as before; pp ) (2) empty table from scratch (pp ) (3) empty table LIKE existing table (pp ) /* (1) CREATE TABLE from query (pp ) create table work.temp1 as select * from cert.sales10; /* no output, but LOG: Table WORK.TEMP1 created, with 4 rows and 4 columns. /* (2) CREATE TABLE as empty table from scratch (pp ) create table work.temp2 (LastName char(9) format=$9., EmplID num, Division char(1), Sales num format=dollar8.); /* no output, but LOG: NOTE: Table WORK.TEMP2 created, with 0 rows and 4 columns. 1

2 /* (3) CREATE TABLE LIKE existing table (pp ) create table work.temp3 like cert.sales10; /* no output, but LOG: NOTE: Table WORK.TEMP3 created, with 0 rows and 4 columns. /* NOTE: To existing (sometimes empty) tables, can later INSERT rows (p. 189) in three ways: (i) SET (by column name; pp ) (ii) VALUES (as lists of values; pp ) (iii) SELECT (from a query; pp ) /* (i) INSERT rows by column name; pp insert into work.temp3 set LastName='Smith', EmplID=315, Division='A', Sales=553312; proc print data=temp3; run; Obs LastName Sales EmplID Division 1 Smith $553, A /* (ii) INSERT rows by list of values; Note that order of column values need not match order in table insert into work.temp3(lastname, EmplID, Division, Sales) values('nelson', 333, 'A', ) values('uribe', 612, 'C', ); Obs LastName Sales EmplID Division proc print data=temp3; run; 1 Smith $553, A 2 Nelson $555, A 3 Uribe $867, C /* (iii) INSERT rows from a query insert into work.temp3 select * from cert.sales10 where LastName='Knecht'; proc print data=temp3; run; Obs LastName Sales EmplID Division 1 Smith $553, A 2 Nelson $555, A 3 Uribe $867, C 4 Knecht $983, B 2

3 /* pp Integrity constraints preserve data validity: CHECK, NOT NULL, UNIQUE, FOREIGN KEY, PRIMARY KEY (both NOT NULL and UNIQUE) Can also name constraints. create table work.temp2 ( LastName char(9) format=$9. not null, EmplID num primary key, Division char(1) check(division in ('A','B','C')), Sales num format=dollar8., constraint pos_sales check (Sales ge 0) ); /* LOG: NOTE: Table WORK.TEMP2 created, with 0 rows and 4 columns. /* What happens if try to insert bad row? insert into work.temp2 set LastName='Smith', EmplID=315, Division='A', Sales= set LastName='Nelson', EmplID=333, Division='D', Sales= ; /* LOG refers to first CHECK failed (Division here) for at least one inserted row, so no rows are inserted. ERROR: Add/Update failed for data set WORK.TEMP2 because data value(s) do not comply with integrity constraint _CK0001_ proc print data=temp2; run;/* No output because 0 rows /* Force inclusion of valid rows with UNDO_POLICY=NONE (pp ) proc sql undo_policy=none; insert into work.temp2 set LastName='Smith', EmplID=315, Division='A', Sales= set LastName='Nelson', EmplID=333, Division='D', Sales= ; proc print data=temp2; run; Obs LastName EmplID Division Sales 2 Smith 315 A $553,312 3

4 /* UPDATE... SET... with same expression (pp ) (Suppose two employees transferred divisions) create table work.temp4 as select EmplID, Division from cert.sales10; update work.temp4 set Division = 'B' where EmplID in (772, 612); proc print data=temp4; run; Obs EmplID Division A A B B B A B B C /* UPDATE... SET... with different expression (pp ) using CASE... WHEN... THEN... <ELSE>... END This is kind of like SELECT... END in Base chapter 10, but more flexible. (Suppose all divisions restructured) create table work.temp4 as select EmplID, Division from cert.sales10; update work.temp4 set Division = case when EmplID in (772, 612) then 'B' when EmplID in (315, 333, 216) then 'A' else 'C' end; proc print data=temp4; run; Obs EmplID Division A A B C A C C B C /* See very efficient CASE example on p

5 /* Can also delete rows (DELETE FROM... WHERE... ; pp ) and add/drop/modify columns (ALTER TABLE ; pp ). Suppose an employee retired and for all remaining employees, their automatic bonus must be reported. create table work.temp4 as select * from cert.sales10; delete from work.temp4 where emplid = 612; alter table work.temp4 add bonus num format=dollar9.2 drop Division modify Sales label='total Annual Sales'; update work.temp4 set bonus =.005*Sales; proc print data=temp4 label; run; Obs LastName Total Annual Sales EmplID bonus 1 Smith $553, $2, Nelson $555, $2, Larson $521, $2, Larsen $123, $ Rasmussen $125, $ Knecht $983, $4, D'Angelou $332, $1, Larson $381, $1, /* To see table definition/composition (including constraints) without reporting all of it, use DESCRIBE TABLE (pp. 182, ); kind of like PROC CONTENTS describe table work.temp4; /* LOG: NOTE: SQL table WORK.TEMP4 was created like: create table WORK.TEMP4( bufsize=65536 ) ( LastName char(9) format=$9., Sales num format=dollar8. label='total Annual Sales', EmplID num, bonus num format=dollar9.2 ); 5

6 /************ Ch. 6 ******************* /* Recall 'indexed' example on p. 10 of Handout #3: focus on efficiency when searching large data sets. p. 240: index stores unique values (and their location in table) for specified column(s). pp : indexes can be helpful but expensive. p. 239: if table is indexed, don't need to search row-by-row such as when using WHEN clause p. 240: It's only worth it to index a table for LARGE data, for columns with many distinct values, and when <15% of rows may be selected for a given query /* p : CREATE INDEX... ON... create index nameind on cert.sales10(emplid, Division); describe table cert.sales10; run; /* LOG: create table cert.sales10( bufsize=65536 ) ( LastName char(9) format=$9., Sales num format=dollar8., EmplID num, Division char(8) ); create index nameind on cert.sales10(emplid,division); /* p. 248: OPTIONS MSGLEVEL=I to check if used. pp : can force or suppress usage of index (using IDXWHERE or IDXNAME), but usually best to let SAS choose (more efficient) select * from cert.sales10 where division='a' & emplid=333; /* no mention of index in LOG LastName Sales EmplID Division options msglevel=i; Nelson $555, A select * from cert.sales10 where division='a' & emplid=333; /* LOG: INFO: Index nameind selected for WHERE clause optimization. options msglevel=n; /* reset 6

7 /* p. 252: DROP INDEX... FROM... drop index nameind from cert.sales10; /* LOG: NOTE: Index nameind has been dropped. /************ Ch. 7 ******************* /* p. 261: PROC SQL view like a pointer (descriptor and other info to retrieve data) to SAS or DBMS files; biggest benefits are to save space (because view just points, doesn't contain data), to protect data (can restrict access to certain columns or rows only included in view), and to ensure users have most current data (because underlying table file can be updated, automatically propogating to all views for downstream users) /* p. 262: CREATE VIEW... AS SELECT... FROM... pp : can treat a view as a table or data set create view cert.tview as select LastName, EmplID, Division from cert.sales10 where division='a'; /* no output, but LOG: NOTE: SQL view WORK.TVIEW has been defined. Creates a tview.sas7bvew file that is MUCH smaller than the cert.sales10 file select * from cert.tview; LastName EmplID Division Smith 315 A Nelson 333 A Rasmussen 217 A D'Angelou 772 A proc print data=cert.tview; run; Obs LastName EmplID Division 1 Smith 315 A 2 Nelson 333 A 3 Rasmussen 217 A 4 D'Angelou 772 A 7

8 /* p. 265: DESCRIBE VIEW -- just like DESCRIBE TABLE (like PROC CONTENTS); DESCRIBE TABLE with a view gives error in LOG describe view cert.tview; /* LOG: NOTE: SQL view cert.tview is defined as: select * from cert.sales10 where division = 'A'; /* p. 266: default LIBREF and embedded USING LIBNAME create view cert.tview as select LastName, EmplID, Division from sales10 /* default LIBREF is same as view's (CERT here) where division='a' using libname cert 'C:/jrstevens/Teaching/SAS_Cert/AdvNotes'; /* in SAS Studio, something like '/home/jrstevens/sas_cert' /* LOG: NOTE: SQL view CERT.TVIEW has been defined. /* pp : UPDATE will actually change the table file (not just the report in SAS) update cert.tview set Division="" where LastName='Rasmussen'; select * from cert.sales10 where LastName='Rasmussen'; LastName Sales EmplID Division Rasmussen $125, /* p. 270: DROP VIEW -- actually deletes the tview.sas7bvew file drop view cert.tview; 8

9 /************ Ch. 8 ******************* /* Options inside PROC SQL statement: INOBS and OUTOBS (p. 280) affect number of read-in and reported rows NUMBER (p. 282) adds column of row number to report STIMER NOSTIMER (p. 286; with PROC OPTIONS, too) sends run-time (statement-wise and total) to LOG DOUBLE (p. 282, for double-spacing) and FLOW (p , for word-wrapping) don't affect HTML output RESET to add/drop/change options in the middle of an SQL execution (p ) LastName Sales EmplID Division Smith $553, A proc options option=stimer value; run; Nelson $555, A D'Angelou $332, A proc sql inobs=10 outobs=3 stimer; select * from cert.sales10 where division='a'; reset number; select * from cert.sales10 where division='b'; Row LastName Sales EmplID Division 1 Larson $521, B 2 Larsen $123, B 3 Knecht $983, B 232 proc sql inobs=10 outobs=3 stimer; NOTE: SQL Statement used (Total process time): real time cpu time 233 select * from cert.sales10 where division='a'; NOTE: SQL Statement used (Total process time): real time cpu time 234 reset number; NOTE: SQL Statement used (Total process time): real time cpu time 235 select * from cert.sales10 where division='b'; NOTE: SQL Statement used (Total process time): real time 0.01 seconds cpu time 236 NOTE: PROCEDURE SQL used (Total process time): real time cpu time 9

10 /* "Dictionary tables", or tables in the DICTIONARY library: summaries of all available libraries, tables, macros, and external files (pp ) -- accessible through SQL queries or sashelp views /* salary10 data cert.salary10; format Salary dollar10.2; input ID Salary; cards; ; proc print data=cert.salary10; run; Obs Salary ID 1 $54, $68, $89, /* Suppose I want to find all variables in all cert library datasets with dollar-related format /* Look inside COLUMNS table describe table dictionary.columns; /* LOG: NOTE: SQL table DICTIONARY.COLUMNS was created like: create table DICTIONARY.COLUMNS ( libname char(8) label='library Name', memname char(32) label='member Name', memtype char(8) label='member Type', name char(32) label='column Name', type char(4) label='column Type', length num label='column Length', npos num label='column Position', varnum num label='column Number in Table', label char(256) label='column Label', format char(49) label='column Format', informat char(49) label='column Informat', idxusage char(9) label='column Index Type', sortedby num label='order in Key Sequence', xtype char(12) label='extended Type', notnull char(3) label='not NULL?', precision num label='precision', scale num label='scale', transcode char(3) label='transcoded?' ); 10

11 select memname, libname, name, format from dictionary.columns where format contains 'DOLLAR' and libname='cert'; /* Note that libname is in all caps Member Name Library Name Column Name Column Format SALARY10 CERT Salary DOLLAR10.2 SALARY8 CERT Salary DOLLAR8. SALARY9 CERT Salary DOLLAR8. SALES10 CERT Sales DOLLAR8. SALES8 CERT Sales DOLLAR8. SALES9 CERT Sales DOLLAR8. /* equivalent but slower: proc print data=sashelp.vcolumn; var memname libname name format; where format contains 'DOLLAR' and libname='cert'; run; Obs memname libname name format 11 SALARY10 CERT Salary DOLLAR SALARY8 CERT Salary DOLLAR8. 17 SALARY9 CERT Salary DOLLAR8. 20 SALES10 CERT Sales DOLLAR8. 24 SALES8 CERT Sales DOLLAR8. 31 SALES9 CERT Sales DOLLAR8. 11

12 /* See pp for list of available tables in DICTIONARY library 12