I had a vendor write a script for us and we are receiving errors pertaining to the line
WHERE 1=1 AND student.calendarID = <selected Calendar>.
I have never seen the syntax "<selected abc>". May someone please explain this to me? Its returning an error for that line as well. I'm using MS SQL Server.
SELECT DISTINCT student.personID
FROM student
join TranscriptCourse tc on tc.personID = student.personID
join TranscriptCourse tc2 on tc2.personID = tc.personID and tc.coursenumber = tc2.coursenumber
WHERE 1=1 AND student.calendarID = <selected Calendar>
AND student.endYear = <selected Year>
AND student.structureID = <selected Schedule>
and tc.gpavalue > 69 and tc2.gpavalue > 69
and tc.transcriptID > tc2.transcriptID
and tc.grade in ('09','10','11','12')
and tc2.grade in ('09','10','11','12')
It looks to me like incorectly used Template Parameters
If used properly in format <parametername, parametertype, defaulvalue> eg <SelectedCalendar, int , 0> you can then use Query > Spefify Values for Template Parameters or Ctrl+Shift+M shortcut and you'll get a window where you can fill values for each template:
Angle brackets are common computer science & software engineering programming language definition meta-characters, aka characters of the notation used to talk about programs, aka a character of a meta-language, aka meta-notation. (Not to be confused with a different meaning for characters treated specially compared to other characters by a system.) In informal communication about programs our metalanguage tends to be natural language plus bits stolen from more formal notations.
Typically <x> means a generic expression of type x that you would replace by program text.
So <selected Schedule> would just mean some language text for a value identifying a a schedule. It's pseudo-code for a parameter.
Related
I have three tables:
PRESS Table : ID, NAME
REGIONS Table : ID, NAME
Each "Press" is published in certain areas (Regions), so I created a child table called "PRESSREGIONS" :
PRESSREGIONS : ID, NAME, IDPRESS
When trying to select records from PRESSREGIONS related to the current PRESS, I use:
SELECT * FROM PRESSREGION WHERE PRESSREGION.IDPRESS = PRESS.ID
I have the following error:
ERROR -206 TOKEN UNKNOWN PRESS.ID
I even tried with another table and another field just to try and got the same error. Is there anything wrong with my statement?
Delphi RIO 10.3 - Firedac - Firebird 3.0
You need to JOIN with PRESS.
SELECT
pr.*,
p.*
FROM
PRESSREGION AS pr
INNER JOIN PRESS AS p ON pr.IDPRESS = p.ID
You can not use PRESS.id because you did not declared PRESS as something you are going to use.
"Translating" to Delphi your queries would look like having two files:
Unit A;
inteface
var AAA: integer;
implementation
end.
and then
Program B;
begin
AAA := 10;
end.
Trying to compile the program - you would receive just the same error, variable AAA was not defined, the token AAA is not known to the Delphi compiler when compiling the module B. Until you either explicitly declare B-local variable AAA or explicitly declare your intention to import AAA variable from the unit A of all existing units (Program B; uses A; ...) - the program would not compile.
If the compiler can not know with absolute warranty what you intended to do - it can not do guesswork and write the program for you by somewhat random estimations.
Same with SQL, unless you explicitly declare the table PRESS (maybe with a shortcut/alias) as something you do have intent to use - the query compiler would not know.
Read chapter chapter 6.1.3. The FROM clause from Firebird documentation.
Or Martin Gruber's "Essential SQL".
Or there were good beginners books for Delphi 3 and Delphi 5 in Russian and probably in other languages too. Actually, "vast and generic scope, shallow depth" beginners books about SQL databases might do better service to you as of yet, than very detailed "narrow scope in-depth" kinds of documentation.
On option to explicitly declare that would be, in SQL'89 flavor "implicit join" way
SELECT * FROM PRESSREGIONs, Press WHERE PRESSREGIONs.IDPRESS = PRESS.ID
Another option, quoted above by Dai, using SQL'92 "explicit join" flavor would be
SELECT * FROM PRESSREGIONs JOIN Press ON PRESSREGIONs.IDPRESS = PRESS.ID
See more SQL commands and Firebird's reactions to them at https://dbfiddle.uk/?rdbms=firebird_3.0&fiddle=8f32007629284cf0aa30128d5a7b5e10
I've seen := used in several code samples, but never with an accompanying explanation. It's not exactly possible to google its use without knowing the proper name for it.
What does it do?
http://en.wikipedia.org/wiki/Equals_sign#In_computer_programming
In computer programming languages, the equals sign typically denotes either a boolean operator to test equality of values (e.g. as in Pascal or Eiffel), which is consistent with the symbol's usage in mathematics, or an assignment operator (e.g. as in C-like languages). Languages making the former choice often use a colon-equals (:=) or ≔ to denote their assignment operator. Languages making the latter choice often use a double equals sign (==) to denote their boolean equality operator.
Note: I found this by searching for colon equals operator
It's the assignment operator in Pascal and is often used in proofs and pseudo-code. It's the same thing as = in C-dialect languages.
Historically, computer science papers used = for equality comparisons and ← for assignments. Pascal used := to stand in for the hard-to-type left arrow. C went a different direction and instead decided on the = and == operators.
In the statically typed language Go := is initialization and assignment in one step. It is done to allow for interpreted-like creation of variables in a compiled language.
// Creates and assigns
answer := 42
// Creates and assigns
var answer = 42
Another interpretation from outside the world of programming languages comes from Wolfram Mathworld, et al:
If A and B are equal by definition (i.e., A is defined as B), then this is written symbolically as A=B, A:=B, or sometimes A≜B.
■ http://mathworld.wolfram.com/Defined.html
■ https://math.stackexchange.com/questions/182101/appropriate-notation-equiv-versus
Some language uses := to act as the assignment operator.
In a lot of CS books, it's used as the assignment operator, to differentiate from the equality operator =. In a lot of high level languages, though, assignment is = and equality is ==.
This is old (pascal) syntax for the assignment operator. It would be used like so:
a := 45;
It may be in other languages as well, probably in a similar use.
A number of programming languages, most notably Pascal and Ada, use a colon immediately followed by an equals sign (:=) as the assignment operator, to distinguish it from a single equals which is an equality test (C instead used a single equals as assignment, and a double equals as the equality test).
Reference: Colon (punctuation).
In Python:
Named Expressions (NAME := expr) was introduced in Python 3.8. It allows for the assignment of variables within an expression that is currently being evaluated. The colon equals operator := is sometimes called the walrus operator because, well, it looks like a walrus emoticon.
For example:
if any((comment := line).startswith('#') for line in lines):
print(f"First comment: {comment}")
else:
print("There are no comments")
This would be invalid if you swapped the := for =. Note the additional parentheses surrounding the named expression. Another example:
# Compute partial sums in a list comprehension
total = 0
values = [1, 2, 3, 4, 5]
partial_sums = [total := total + v for v in values]
# [1, 3, 6, 10, 15]
print(f"Total: {total}") # Total: 15
Note that the variable total is not local to the comprehension (so too is comment from the first example). The NAME in a named expression cannot be a local variable within an expression, so, for example, [i := 0 for i, j in stuff] would be invalid, because i is local to the list comprehension.
I've taken examples from the PEP 572 document - it's a good read! I for one am looking forward to using Named Expressions, once my company upgrades from Python 3.6. Hope this was helpful!
Sources: Towards Data Science Article and PEP 572.
It's like an arrow without using a less-than symbol <= so like everybody already said "assignment" operator. Bringing clarity to what is being set to where as opposed to the logical operator of equivalence.
In Mathematics it is like equals but A := B means A is defined as B, a triple bar equals can be used to say it's similar and equal by definition but not always the same thing.
Anyway I point to these other references that were probably in the minds of those that invented it, but it's really just that plane equals and less that equals were taken (or potentially easily confused with =<) and something new to define assignment was needed and that made the most sense.
Historical References: I first saw this in SmallTalk the original Object Language, of which SJ of Apple only copied the Windows part of and BG of Microsoft watered down from them further (single threaded). Eventually SJ in NeXT took the second more important lesson from Xerox PARC in, which became Objective C.
Well anyway they just took colon-equals assiment operator from ALGOL 1958 which was later popularized by Pascal
https://en.wikipedia.org/wiki/PARC_(company)
https://en.wikipedia.org/wiki/Assignment_(computer_science)
Assignments typically allow a variable to hold different values at
different times during its life-span and scope. However, some
languages (primarily strictly functional) do not allow that kind of
"destructive" reassignment, as it might imply changes of non-local
state.
The purpose is to enforce referential transparency, i.e. functions
that do not depend on the state of some variable(s), but produce the
same results for a given set of parametric inputs at any point in
time.
https://en.wikipedia.org/wiki/Referential_transparency
For VB.net,
a constructor (for this case, Me = this in Java):
Public ABC(int A, int B, int C){
Me.A = A;
Me.B = B;
Me.C = C;
}
when you create that object:
new ABC(C:=1, A:=2, B:=3)
Then, regardless of the order of the parameters, that ABC object has A=2, B=3, C=1
So, ya, very good practice for others to read your code effectively
Colon-equals was used in Algol and its descendants such as Pascal and Ada because it is as close as ASCII gets to a left-arrow symbol.
The strange convention of using equals for assignment and double-equals for comparison was started with the C language.
In Prolog, there is no distinction between assignment and the equality test.
I'm trying to write a language independent filter for MS Project in VBA. I'm using the syntax:
FilterEdit (Name, Taskfilter, Create, Fieldname, Test, Value, Operation...)
I have managed to get the Fieldnames and Tests to be language independent, but I struggle with the Operation:= expression. For an English locale one would write: Operation:="and" but that doesnt work for other locales.
Is there a way to write the logical operator (and/or) as an enumeration? (not as a string?)
For Excel one could write xlAnd, and Project has a lot of enumerations starting with Pj, ie. PjTaskStart. I also know there's a Filter.LogicalOperationType, but I haven't managed to figure out if this could work for me or not. I have also experimented with FieldConstantToFieldName, but I reckon there's no fieldname for the logical operator?
I know I could use If LocaleID = xxxx Then..., but I'd like to not assume what locales will be in use.
Edit: I solved the first part of my problem!
By leaving it blank Operation:="", Project returns "And". But I haven't figured out yet how to return "Or"...
Operation:="" works for FilterEdit, but not for SetAutoFilter.
So I ended up using the dreaded If LocaleID.
Teaching moment:
I found out most operators can be language independent, except for:
And, Or, Contains and Does Not Contain.
These needs to be translated for each locale. I'll get to those in a minute. First I'll list all the language independent operators:
< Less than <= Less than or equal to > Greater than >= Greater than or equal to = Equal to <> Not equal to
My trick for finding the translations I need for the language dependent operators is the following MS Office Support page.
Notice the category named "Filter for specific text" in the English support page. Here we can read all the "words" we need. Now go to the bottom of the web page and change the language:
This opens up a new page listing all the different languages (not locale specific). Remembering where you found the word for Contains in English, then changing the language to for instance "Magyar (Magyarorzág)", we can now see that Contains = "Tartalmazza" in Magyar.
Next step is to google "Magyar languge" and learn that this actually equals Hungarian. So now you can go to this MSDN web page to see that Hungarian = LocaleID: 1038.
Putting all this together inside VBA makes you have to write the following code:
Dim LocalContains As String
If LocaleID = 1038 Then
LocalContains = "Tartalmazza" 'Hungarian
ElseIf LocaleID = 1044 Then
LocalContains = "inneholder" 'Norwegian
Else
LocalContains = "contains" 'English
End If
So, I'm writing a language using flex/bison and I'm having difficulty with implementing identifiers, specifically when it comes to knowing when you're looking at an assignment or a reference,
for example:
1) A = 1+2
2) B + C (where B and C have already been assigned values)
Example one I can work out by returning an ID token from flex to bison, and just following a grammar that recognizes that 1+2 is an integer expression, putting A into the symbol table, and setting its value.
examples two and three are more difficult for me because: after going through my lexer, what's being returned in ex.2 to bison is "ID PLUS ID" -> I have a grammar that recognizes arithmetic expressions for numerical values, like INT PLUS INT (which would produce an INT), or DOUBLE MINUS INT (which would produce a DOUBLE). if I have "ID PLUS ID", how do I know what type the return value is?
Here's the best idea that I've come up with so far: When tokenizing, every time an ID comes up, I search for its value and type in the symbol table and switch out the ID token with its respective information; for example: while tokenizing, I come across B, which has a regex that matches it as being an ID. I look in my symbol table and see that it has a value of 51.2 and is a DOUBLE. So instead of returning ID, with a value of B to bison, I'm returning DOUBLE with a value of 51.2
I have two different solutions that contradict each other. Here's why: if I want to assign a value to an ID, I would say to my compiler A = 5. In this situation, if I'm using my previously described solution, What I'm going to get after everything is tokenized might be, INT ASGN INT, or STRING ASGN INT, etc... So, in this case, I would use the former solution, as opposed to the latter.
My question would be: what kind of logical device do I use to help my compiler know which solution to use?
NOTE: I didn't think it necessary to post source code to describe my conundrum, but I will if anyone could use it effectively as a reference to help me understand their input on this topic.
Thank you.
The usual way is to have a yacc/bison rule like:
expr: ID { $$ = lookupId($1); }
where the the lookupId function looks up a symbol in the symbol table and returns its type and value (or type and storage location if you're writing a compiler rather than a strict interpreter). Then, your other expr rules don't need to care whether their operands come from constants or symbols or other expressions:
expr: expr '+' expr { $$ = DoAddition($1, $3); }
The function DoAddition takes the types and values (or locations) for its two operands and either adds them, producing a result, or produces code to do the addition at run time.
If possible redesign your language so that the situation is unambiguous. This is why even Javascript has var.
Otherwise you're going to need to disambiguate via semantic rules, for example that the first use of an identifier is its declaration. I don't see what the problem is with your case (2): just generate the appropriate code. If B and C haven't been used yet, a value-reading use like this should be illegal, but that involves you in control flow analysis if taken to the Nth degree of accuracy, so you might prefer to assume initial values of zero.
In any case you can see that it's fundamentally a language design problem rather than a coding problem.
I have this scenario where I need data integrity in the physical database. For example, I have a variable of #email_address VARCHAR(200) and I want to check if the value of #email_address is of email format. Anyone has any idea how to check format in T-SQL?
Many thanks!
I tested the following query with many different wrong and valid email addresses. It should do the job.
IF (
CHARINDEX(' ',LTRIM(RTRIM(#email_address))) = 0
AND LEFT(LTRIM(#email_address),1) <> '#'
AND RIGHT(RTRIM(#email_address),1) <> '.'
AND CHARINDEX('.',#email_address ,CHARINDEX('#',#email_address)) - CHARINDEX('#',#email_address ) > 1
AND LEN(LTRIM(RTRIM(#email_address ))) - LEN(REPLACE(LTRIM(RTRIM(#email_address)),'#','')) = 1
AND CHARINDEX('.',REVERSE(LTRIM(RTRIM(#email_address)))) >= 3
AND (CHARINDEX('.#',#email_address ) = 0 AND CHARINDEX('..',#email_address ) = 0)
)
print 'valid email address'
ELSE
print 'not valid'
It checks these conditions:
No embedded spaces
'#' can't be the first character of an email address
'.' can't be the last character of an email address
There must be a '.' somewhere after '#'
the '#' sign is allowed
Domain name should end with at least 2 character extension
can't have patterns like '.#' and '..'
AFAIK there is no good way to do this.
The email format standard is so complex parsers have been known to run to thousands of lines of code, but even if you were to use a simpler form which would fail some obscure but valid addresses you'd have to do it without regular expressions which are not natively supported by T-SQL (again, I'm not 100% on that), leaving you with a simple fallback of somethign like:
LIKE '%_#_%_.__%'
..or similar.
My feeling is generally that you shouln't be doing this at the last possible moment though (as you insert into a DB) you should be doing it at the first opportunity and/or a common gateway (the controller which actually makes the SQL insert request), where incidentally you would have the advantage of regex, and possibly even a library which does the "real" validation for you.
If you use SQL 2005 or 2008 you might want to look at writing CLR stored proceudues and use the .NET regex engine like this. If you're using SQL 2000 or earlier you can use the VBScript scripting engine's regular expression like ths. You could also use an extended stored procedure like this
There is no easy way to do it in T-SQL, I am afraid. To validate all the varieties of email address allowed byRFC 2822 you will need to use a regular expression.
More info here.
You will need to define your scope, if you want to simplify it.