Corona Lua SQLite - sql

Question

this is my first question on stackOverflow.
I'm working with Corona and I'm having an issue accessing a SQLdb (I'm a bit of a SQL noob.)
I'm trying to access and return a value I've stored in the database.
Here's some code samples:
print("---------------- How I Create New Player Save Data")
local entry = [[CREATE TABLE IF NOT EXISTS playerData (key STRING PRIMARY KEY, content INTEGER);]]
db:exec(entry)
entry = [[INSERT INTO playerData VALUES ("LastLoginTime", 0);]]
db:exec( entry )
entry = [[INSERT INTO playerData VALUES ("Credits", 1000);]]
db:exec( entry )
entry = [[INSERT INTO playerData VALUES ("Level", 1);]]
db:exec( entry )
Now this function works, it will print everything in the db (i pass in 'dbName'):
--print all the table contents
for row in db:nrows("SELECT * FROM "..dbName) do
local text = row.key..": "..row.content
end
This doesn't work, it returns '0':
local grabCredits = "SELECT content FROM playerData WHERE key='Credits'"
local credits = db:exec(grabCredits)
print("-- value: "..credits)
Neither does this, also returns '0':
local grabCredits = "SELECT key FROM playerData WHERE content>=10"
local credits = db:exec(grabCredits)
print("-- value: "..credits)
I don't understand what I'm doing wrong. Maybe I need to use another function call on the db other than exec(). I realize I could iterate through the db every time I want to access a single entry, but that just seems inefficient.
Any help is very much appreciated.

Answer 1

If you want results, you must use some form of iterator. SQLite always returns rows for a query result.

Answer 2

This is similar to what I'm using to retrieve one result from my database and works well for me.
local query = "SELECT content FROM playerData WHERE key = 'Credits' LIMIT 1"
local queryResultTable = {}
local queryFunction = function(userData, numberOfColumns, columnValues, columnTitles)
for i = 1, numberOfColumns do
queryResultTable[columnTitles[i]] = columnValues[i]
end
end
db:exec(query, queryFunction)
for k,v in pairs(queryResultTable) do
print(k,v)
end