Takusen and inserting type Maybe with sqlite3
Hello, I'm stumped on using Takusen to insert values of type Maybe into a sqlite database when the underlying database has a field type of REAL. When I bind a Maybe to an underlying sqlite field of type DATETIME or INTEGER, the value is stored correctly. However, when I bind a Maybe value to a database field of type REAL, the value is inserted as "Just ..." or "Nothing". I thought bindP would coerce the Maybe type either into the value or a database null. What am I missing? Here is an example of an inserted record in the database: sqlite> select * from summary; 20110331|100002|Just 0.37427717861180376|Just 2.198753718609092|Just 9.402720712996771|Just 17.50143032492688|Just 8.250653601136904|Nothing|Nothing|Just 6.190434991035554 Here is the function: storeSummary date account returns = do dbh <- openDb withSession dbh (do execDML(cmdbind "REPLACE INTO summary (date,account_id,one_mo,three_mo,one_yr,two_yr,three_yr,four_yr,five_yr,incept) \ \VALUES (?,?,?,?,?,?,?,?,?,?)" [bindP (Just date), bindP (Just account), bindP (returns !! 0),bindP (returns !! 1),bindP (returns !! 2),bindP (returns !! 3), bindP (returns !! 4),bindP (returns !! 5),bindP (returns !! 6),bindP (returns !! 7) ]) ) And the database: sqlite>.schema summary CREATE TABLE "SUMMARY" ("DATE" DATETIME NOT NULL ,"ACCOUNT_ID" INTEGER NOT NULL ,"ONE_MO" REAL,"THREE_MO" REAL,"ONE_YR" REAL,"TWO_YR" REAL,"THREE_YR" REAL,"FOUR_YR" REAL,"FIVE_YR" REAL,"INCEPT" REAL, PRIMARY KEY ("DATE","ACCOUNT_ID") ) Thanks in advance, Neil
I just answered my own question... I had forgotten the type signature on the
storeSummary function. When I added the type signature below, it coerced the
Maybe RoR (which is a Double) into a REAL in sqlite3.
storeSummary :: ISODateInt -> AccountId -> [Maybe RoR] -> IO Int
Problem solved.
Neil
On Fri, May 13, 2011 at 2:35 PM, Neil Jensen
Hello, I'm stumped on using Takusen to insert values of type Maybe into a sqlite database when the underlying database has a field type of REAL.
When I bind a Maybe to an underlying sqlite field of type DATETIME or INTEGER, the value is stored correctly. However, when I bind a Maybe value to a database field of type REAL, the value is inserted as "Just ..." or "Nothing".
I thought bindP would coerce the Maybe type either into the value or a database null. What am I missing?
Here is an example of an inserted record in the database:
sqlite> select * from summary; 20110331|100002|Just 0.37427717861180376|Just 2.198753718609092|Just 9.402720712996771|Just 17.50143032492688|Just 8.250653601136904|Nothing|Nothing|Just 6.190434991035554
Here is the function:
storeSummary date account returns = do dbh <- openDb withSession dbh (do execDML(cmdbind "REPLACE INTO summary (date,account_id,one_mo,three_mo,one_yr,two_yr,three_yr,four_yr,five_yr,incept) \ \VALUES (?,?,?,?,?,?,?,?,?,?)" [bindP (Just date), bindP (Just account),
bindP (returns !! 0),bindP (returns !! 1),bindP (returns !! 2),bindP (returns !! 3),
bindP (returns !! 4),bindP (returns !! 5),bindP (returns !! 6),bindP (returns !! 7) ]) )
And the database:
sqlite>.schema summary CREATE TABLE "SUMMARY" ("DATE" DATETIME NOT NULL ,"ACCOUNT_ID" INTEGER NOT NULL ,"ONE_MO" REAL,"THREE_MO" REAL,"ONE_YR" REAL,"TWO_YR" REAL,"THREE_YR" REAL,"FOUR_YR" REAL,"FIVE_YR" REAL,"INCEPT" REAL, PRIMARY KEY ("DATE","ACCOUNT_ID") )
Thanks in advance, Neil
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Neil Jensen