Appendix B Citadel and Open Database Connectivity
BridgeVIEW User Manual B-6 © National Instruments Corporation
Assume, for example, that you want to find out how many times a
compressor motor started in December. You also want to know its total
runtime for the month. The following query provides the answers:
SELECT "Starts{MotorRun}",
"ETM{MotorRun}"
FROM Threads
WHERE LocalTime >= "12/1/95"
AND LocalTime < "1/1/96"
AND Interval = "31"
SQL Examples
The following examples are typical query statements; however, your
queries may be much more involved, depending on your system
requirements.
• Retrieves the most recent (current) value of every tag logged to
Citadel.
SELECT *
FROM Threads
• Retrieves the value of every tag logged today in one second
increments. Note the interval value is specified within
quotation marks.
SELECT *
FROM Threads
WHERE Interval=“0:01”
• Retrieves and time-stamps the value of Powder in one second
increments from 8:50 this morning to now. Tag names are surrounded
by quotes.
SELECT LocalTime, “Powder”
FROM Threads
WHERE LocalTime>“8:50”
AND Interval=“0:01”
• Retrieves and time-stamps the value of Liquid input in one minute
intervals for the month of October. Also indicates the input’s highest
occurring value within each minute.
SELECT LocalTime, “Liquid”, “Max{Liquid}”
FROM Threads
WHERE LocalTime>“10/1/96”
AND LocalTime<“11/1/96”
AND Interval=“1:00”