Passing an array to sqlite WHERE IN clause via FMDB? - ios

Question

Is it possible to pass an array to a SELECT … WHERE … IN statement via FMDB?
I tried to implode the array like this:
NSArray *mergeIds; // An array with NSNumber Objects
NSString *mergeIdString = [mergeIds componentsJoinedByString:#","];
NSString *query = #"SELECT * FROM items WHERE last_merge_id IN (?)";
FMResultSet *result = [database executeQuery:query, mergeIdString];
This only works if there is exactly 1 object in the array, which leads me to believe that FMDB adds quotes around the whole imploded string.
So I tried passing the array as is to FMDB's method:
NSArray *mergeIds; // An array with NSNumber Objects
NSString *query = #"SELECT * FROM items WHERE last_merge_id IN (?)";
FMResultSet *result = [database executeQuery:query, mergeIds];
Which doesn't work at all.
I didn't find anything about it in the README or the samples on FMDB's github page.
Thanks, Stefan

Answer 1

I was having the same issue, and I figured it out, at least for my own app. First, structure your query like so, matching the number of question marks as the amount of data in the array:
NSString *getDataSql = #"SELECT * FROM data WHERE dataID IN (?, ?, ?)";
Then use the executeQuery:withArgumentsInArray call:
FMResultSet *results = [database executeQuery:getDataSql withArgumentsInArray:dataIDs];
In my case, I had an array of NSString objects inside the NSArray named dataIDs. I tried all sorts of things to get this SQL query working, and finally with this combination of sql / function call, I was able to get proper results.

Answer 2

Well I guess I have to use executeQueryWithFormat (which, according to FMDB documentation is not the recommended way). Anyway, here's my solution:
NSArray *mergeIds; // An array of NSNumber Objects
NSString *mergeIdString = [mergeIds componentsJoinedByString:#","];
NSString *query = #"SELECT * FROM items WHERE last_merge_id IN (?)";
FMResultSet *res = [self.database executeQueryWithFormat:query, mergeIdString];

Answer 3

Adding onto Wayne Liu, if you know that the strings do not contain single or double quotes, you could simply do:
NSString * delimitedString = [strArray componentsJoinedByString:#"','"];
NSString * sql = [NSString stringWithFormat:#"SELECT * FROM tableName WHERE fieldName IN ('%#')", delimitedString];

Answer 4

If the keys are strings, I use the following code to generate the SQL command:
(assume strArray is an NSArray containing NSString elements)
NSString * strComma = [strArray componentsJoinedByString:#"\", \""];
NSString * sql = [NSString stringWithFormat:#"SELECT * FROM tableName WHERE fieldName IN (\"%#\")", strComma];
Please note: if any elements in strArray could potentially contain the "double quote" symbols, you need to write extra codes (before these 2 lines) to escape them by writing 2 double quotes instead.

Answer 5

I created a simple FMDB extension to solve the problem:
FMDB+InOperator on GitHub

Answer 6

Here's a Swift extension for FMDatabase that breaks array query parameters into multiple named parameters.
extension FMDatabase {
func executeQuery(query: String, params:[String: AnyObject]) -> FMResultSet? {
var q = query
var d = [String: AnyObject]()
for (key, val) in params {
if let arr = val as? [AnyObject] {
var r = [String]()
for var i = 0; i < arr.count; i++ {
let keyWithIndex = "\(key)_\(i)"
r.append(":\(keyWithIndex)")
d[keyWithIndex] = arr[i]
}
let replacement = ",".join(r)
q = q.stringByReplacingOccurrencesOfString(":\(key)", withString: "(\(replacement))", options: NSStringCompareOptions.LiteralSearch, range: nil)
}
else {
d[key] = val
}
}
return executeQuery(q, withParameterDictionary: d)
}
}
Example:
let sql = "SELECT * FROM things WHERE id IN :thing_ids"
let rs = db.executQuery(sql, params: ["thing_ids": [1, 2, 3]])