How to use dynamic variable in RMySQL LIKE Statement [duplicate] - mysql

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Closed 5 years ago.
Is there any way to pass a variable defined within R to the sqlQuery function within the RODBC package?
Specifically, I need to pass such a variable to either a scalar/table-valued function, a stored procedure, and/or perhaps the WHERE clause of a SELECT statement.
For example, let:
x <- 1 ## user-defined
Then,
example <- sqlQuery(myDB,"SELECT * FROM dbo.my_table_fn (x)")
Or...
example2 <- sqlQuery(myDB,"SELECT * FROM dbo.some_random_table AS foo WHERE foo.ID = x")
Or...
example3 <- sqlQuery(myDB,"EXEC dbo.my_stored_proc (x)")
Obviously, none of these work, but I'm thinking that there's something that enables this sort of functionality.

Answer 1

Build the string you intend to pass. So instead of
example <- sqlQuery(myDB,"SELECT * FROM dbo.my_table_fn (x)")
do
example <- sqlQuery(myDB, paste("SELECT * FROM dbo.my_table_fn (",
x, ")", sep=""))
which will fill in the value of x.

Answer 2

If you use sprintf, you can very easily build the query string using variable substitution. For extra ease-of-use, if you pre-parse that query string (I'm using stringr) you can write it over multiple lines in your code.
e.g.
q1 <- sprintf("
SELECT basketid, count(%s)
FROM %s
GROUP BY basketid
"
,item_barcode
,dbo.sales
)
q1 <- str_replace_all(str_replace_all(q1,"\n",""),"\\s+"," ")
df <- sqlQuery(shopping_database, q1)
Side-note and hat-tip to another R chap
Recently I found I wanted to make the variable substitution even simpler by using something like Python's string.format() function, which lets you reuse and reorder variables within the string
e.g.
$: w = "He{0}{0}{1} W{1}r{0}d".format("l","o")
$: print(w)
"Hello World"
However, this function doesn't appear to exist in R, so I asked around on Twitter, and a very helpful chap #kevin_ushey replied with his own custom function to be used in R. Check it out!

Answer 3

With more variables do this:
aaa <- "
SELECT ColOne, ColTwo
FROM TheTable
WHERE HpId = AAAA and
VariableId = BBBB and
convert (date,date ) < 'CCCC'
"
--------------------------
aaa <- gsub ("AAAA", toString(111),aaa)
aaa <- gsub ("BBBB", toString(2222),aaa)
aaa <- gsub ("CCCC", toString (2016-01-01) ,aaa)

Answer 4

try with this
x <- 1
example2 <- fn$sqlQuery(myDB,"SELECT * FROM dbo.some_random_table AS foo WHERE foo.ID = '$x'")