Using both mclient and C#/C++ test clients connected via 64bit ODBC I am encountering this type mismatch error for no obvious reason. This is something of a show-stopper for what had proved to be a very interesting experiment! # MonetDB 5 server v11.19.3 "Oct2014" # Serving database 'dbfarm', using 4 threads # Compiled for x86_64-pc-winnt/64bit with 64bit OIDs dynamically linked # Found 15.982 GiB available main-memory. An example query below, weight is a double, all other columns are integer. There are no NULL values, nor any oddities sql>SELECT count(weight) , sum(weight) , avg(weight) , stddev_pop(weight) FROM test_1 WHERE ((severity = 1 OR severity = 2) AND (iat = 2) AND (ilit = 3)); Type mismatch But a family of closely related queries do succeed: sql>SELECT count(weight) , sum(weight) , avg(weight) , stddev_pop(weight) FROM test_1 WHERE ((severity = 1 OR severity = 2) AND (iat = 2) AND (ilit = 11)); | L1 | L2 | L3 |> | 290517 | 290517 | 1 | 1 tuple (200.115ms) !1 column dropped! Enabling ODBC logging does not reveal a great deal more than this: dbc-con.vshost 13d8-2ac4 ENTER SQLExecDirectW HSTMT 0x000000000048F370 WCHAR * 0x000000000256458C [ -3] "SELECT count(weight) as cnt, sum(weight) as total, avg(weight) as average, stddev_pop(weight) as stddev FROM test_1 WHERE ((severity = 1 OR severity = 2) AND (iat = 2) AND (ilit = 3))\ 0" SDWORD -3 odbc-con.vshost 13d8-2ac4 EXIT SQLExecDirectW with return code -1 (SQL_ERROR) HSTMT 0x000000000048F370 WCHAR * 0x000000000256458C [ -3] "SELECT count(weight) as cnt, sum(weight) as total, avg(weight) as average, stddev_pop(weight) as stddev FROM test_1 WHERE ((severity = 1 OR severity = 2) AND (iat = 2) AND (ilit = 3))\ 0" SDWORD -3 DIAG [HY000] [MonetDB][ODBC Driver 11.19.3]Type mismatch (0) odbc-con.vshost 13d8-2ac4 ENTER SQLGetDiagRecW SQLSMALLINT 3 <SQL_HANDLE_STMT> SQLHANDLE 0x000000000048F370 SQLSMALLINT 1 SQLWCHAR * 0x000000001C39D940 SQLINTEGER * 0x000000001C39DB34 SQLWCHAR * 0x000000001B6246C0 SQLSMALLINT 1024 SQLSMALLINT * 0x000000001C39DB30 odbc-con.vshost 13d8-2ac4 EXIT SQLGetDiagRecW with return code 0 (SQL_SUCCESS) SQLSMALLINT 3 <SQL_HANDLE_STMT> SQLHANDLE 0x000000000048F370 SQLSMALLINT 1 SQLWCHAR * 0x000000001C39D940 [ 5] "HY000" SQLINTEGER * 0x000000001C39DB34 (0) SQLWCHAR * 0x000000001B6246C0 [ 43] "[MonetDB][ODBC Driver 11.19.3]Type mismatch" SQLSMALLINT 1024 SQLSMALLINT * 0x000000001C39DB30 (43)