The values in the coltype column of the syscolumns system catalog table are defined primarily in the Informix ESQL/C header sqltypes.h. This header is used throughout the Informix server code.
The values in the coltype column are a mixture of an 8-bit (unsigned) integer in the low-order bits, and various flag values in the high-order bits. In particular, when a column is defined with the NOT NULL qualifier, the 0x100 bit is set — which corresponds to 'add 256'. There are other flag bits which you are less likely to see.
The value 4118 (decimal) shown in another answer corresponds to hex 0x1016; the 16 (aka 22 decimal) corresponds to SQLROW, and the 0x1000 (4096 decimal) bit corresponds to #define SQLNAMED 0x1000 /* Named row type vs row type */. The type is (as noted in the other answer) a 'named row type'.
Consider a table:
CREATE TABLE bool_check
(
b1 BOOLEAN NOT NULL,
b2 BOOLEAN
);
The values in the sqltype column of syscolumns are:
b1 = 297 = 256 + 41b2 = 41
These correspond to SQLUDTFIXED (type 41). The type SQLBOOL is marked 'used by FE [front end], … not real major types in BE [back end, meaning database server]'. The collength is 1 for both.
Relevant segments of the header include:
SQL Types:
#define SQLCHAR 0
#define SQLSMINT 1
#define SQLINT 2
#define SQLFLOAT 3
#define SQLSMFLOAT 4
#define SQLDECIMAL 5
#define SQLSERIAL 6
#define SQLDATE 7
#define SQLMONEY 8
#define SQLNULL 9
#define SQLDTIME 10
#define SQLBYTES 11
#define SQLTEXT 12
#define SQLVCHAR 13
#define SQLINTERVAL 14
#define SQLNCHAR 15
#define SQLNVCHAR 16
#define SQLINT8 17
#define SQLSERIAL8 18
#define SQLSET 19
#define SQLMULTISET 20
#define SQLLIST 21
#define SQLROW 22
#define SQLCOLLECTION 23
#define SQLROWREF 24
/*
* Note: SQLXXX values from 25 through 39 are reserved to avoid collision
* with reserved PTXXX values in that same range. See p_types_t.h
*
* REFSER8: create tab with ref: referenced serial 8 rsam counter
* this is essentially a SERIAL8, but is an additional rsam counter
* this type only lives in the system catalogs and when read from
* disk is converted to SQLSERIAL8 with CD_REFSER8 set in ddcol_t
* ddc_flags we must distinguish from SERIAL8 to allow both
* counters in one tab
*
* SQLSTREAM: Is a synonym for SQLUDTFIXED used by CDR (Enterprise
* Replication) code
*/
#define SQLUDTVAR 40
#define SQLUDTFIXED 41
#define SQLSTREAM SQLUDTFIXED
#define SQLREFSER8 42
/* These types are used by FE, they are not real major types in BE */
#define SQLLVARCHAR 43
#define SQLSENDRECV 44
#define SQLBOOL 45
#define SQLIMPEXP 46
#define SQLIMPEXPBIN 47
/* This type is used by the UDR code to track default parameters,
it is not a real major type in BE */
#define SQLUDRDEFAULT 48
#define SQLUNKNOWN 51
#define SQLBIGINT 52
#define SQLBIGSERIAL 53
#define SQLMAXTYPES 54
#define SQLLABEL SQLINT
Flags:
#define SQLNONULL 0x0100 /* disallow nulls */
/* a bit to show that the value is from a host variable */
#define SQLHOST 0x0200 /* Value is from host var. */
#define SQLNETFLT 0x0400 /* float-to-decimal for networked backend */
#define SQLDISTINCT 0x0800 /* distinct bit */
#define SQLNAMED 0x1000 /* Named row type vs row type */
#define SQLDLVARCHAR 0x2000 /* Distinct of lvarchar */
#define SQLDBOOLEAN 0x4000 /* Distinct of boolean */
#define SQLCLIENTCOLL 0x8000 /* Collection is processed on client */
/* we are overloading SQLDBOOLEAN for use with row types */
#define SQLVARROWTYPE 0x4000 /* varlen row type */
There are also 'C-ISAM types' with numbers 100 to 125 and names such a CCHARTYPE and CDECIMALTYPE. They are not of immediate concern here. There are 524 lines in the header file (at least in the version I looked at). Of those, 74 are blank, 315 contain code, and the remaining lines are pure comment lines. AFAIK, the SQLREFSER8 type is stillborn; it does not exist outside this file.
The types BLOB NOT NULL and CLOB NOT NULL are both encoded in coltype as 297 (41 + 256 — the same a BOOLEAN NOT NULL), or SQLUDTFIXED with collength of 72 (as opposed to 1 for BOOLEAN NOT NULL). The fixed-length data is a descriptor that provides all the details about where the BLOB or CLOB value is actually stored.
