hsSqlExTimeCond: SQL Expression: Time Period

In KWB-R/kwb.db: Functions supporting data base access

SQL Expression: Time Period

Description

WHERE-condition string in MS Jet SQL syntax filtering for a specific time interval

Usage

hsSqlExTimeCond(
  tsField,
  dateFirst = NULL,
  dateLast = NULL,
  inclLast = TRUE,
  sqlDialect = getCurrentSqlDialect(),
  dbg = FALSE
)

Arguments

tsField	name of timestamp field
dateFirst	Date object representing the first date of the time interval to be selected.
dateLast	Date object representing the last date of the time interval to be selected.
inclLast	if TRUE, dateLast will be included in result data set, else excluded.
sqlDialect	one of c("mysql", "msaccess")
dbg	if TRUE, debug messages are shown

Value

Condition string in MS Jet SQL syntax to be used in WHERE clause

See Also

hsJetDate

Examples

## Not run: 
## Condition string to filter field "datetime" for timestamps 
## between 21 and 22 of July 2010
from <- as.Date("2011-08-23")
to   <- as.Date("2011-08-24")
cond <- hsSqlExTimeCond("Zeitst", from, to)
cond  
  
## Output:
# TRUE  AND Zeitst >= #08/23/2011 00:00:00#  
#       AND Zeitst <= #08/24/2011 00:00:00#
  
## The condition string may now be used in an SQL query 
## to select data from within the time interval. 
sql <- sprintf("SELECT * FROM tbl_Hyd WHERE %s", cond)

if (.Platform$OS.type == "windows") {

  res <- hsSqlQuery(xmdb(), sql)
  head(res)
}
   
## Output:
# Zeitst Q v     H T_Kanal
# 1 2011-08-23 00:00:00 0 0 1.260    19.5
# 2 2011-08-23 00:01:00 0 0 1.259    19.5
# 3 2011-08-23 00:02:00 0 0 1.259    19.5
# 4 2011-08-23 00:03:00 0 0 1.259    19.5
# 5 2011-08-23 00:04:00 0 0 1.260    19.5
# 6 2011-08-23 00:05:00 0 0 1.260    19.5

## End(Not run)

KWB-R/kwb.db documentation built on Oct. 1, 2023, 4:10 a.m.