2.4 Expressions

Although all DBTools.h++ access libraries are implemented through the same interface, there are differences in the parameters that must be passed to certain expressions. The following section outlines the differences in the DB2 CLI access library.

2.4.1 Global Functions

DBTools.h++ provides a predefined set of global functions, which allow an application to build portable SQL expressions. Table 3 lists restrictions on the global functions associated with RWDBExpr.

Table 3 -- Restrictions on the use of global functions with RWDBExpr

Function	Restrictions
`rwdbAvg(const RWDBExpr&)`	None. Corresponds to: `AVG(expr)`
`rwdbCast(const RWDBExpr&, const RWDBValue&)`	None. Corresponds to: `{fn CONVERT(expr, expr)}`
`rwdbCast(const RWDBExpr&, const RWDBValue&, const RWDBExpr&)`	Same as the two-expression form, as DB2 does not support this form.
`rwdbCast(const RWBDExpr&, const RWDBValue&, const RWDBExpr&, const RWDBExpr&)`	Same as the two-expression form, as DB2 does not support this form.
`rwdbCharLength(const RWDBExpr&)`	None. Corresponds to: `{fn LENGTH(expr)}`
rwdbCount(*)	None. Corresponds to: `COUNT(*)`
`rwdbCount(const RWDBExpr&)`	None. Corresponds to: `COUNT(expr)`
`rwdbCountDistinct(const RWDBExpr&)`	None. Corresponds to: `COUNT(DISTINCT expr)`
`rwdbCurrentUser()`	None. Corresponds to: `{fn USER ()}`
`rwdbExists(const RWDBSelectorBase&)`	None. Corresponds to: `EXISTS sel`
`rwdbLower(const RWDBExpr&)`	None. Corresponds to: `{fn LCASE(expr)}`
`rwdbMax(const RWDBExpr&)`	None. Corresponds to: `MAX(expr)`
`rwdbMin(const RWDBExpr&)`	None. Corresponds to: `MIN(expr)`
`rwdbName(const RWCString&, const RWDBExpr&)`	None. Corresponds to: `expr = expr`
`rwdbPosition(const RWDBExpr&, const RWDBExpr&)`	None. Corresponds to: `{fn LOCATE(expr, expr)}`
`rwdbSessionUser()`	None. Corresponds to: `{fn USER() }`
`rwdbSubString(const RWDBExpr&, const RWDBExpr&)`	None. Corresponds to: `{fn SUBSTRING (expr0, expr1, fn LENGTH(expr0))}`
`rwdbSubString(const RWDBExpr&, const RWDBExpr&, const RWDBExpr&)`	None. Corresponds to: `{fn SUBSTRING(expr0, expr1, expr2)}`
`rwdbSum(const RWDBExpr&)`	None. Corresponds to: `SUM(expr)`
rwdbSystemDateTime()	None. Corresponds to: `{ fn NOW() }`
`rwdbSystemUser()`	None. Corresponds to: `{ fn USER() }`
`rwdbTrimLeading(const RWDBExpr&, const RWDBExpr&)`	None. Default from the core library: `TRIM(LEADING expr FROM expr)`
`rwdbTrimTrailing(const RWDBExpr&, const RWDBExpr&)`	None. Default from the core library:`TRIM(TRAILING expr FROM expr)`
`rwdbTrimBoth(const RWDBExpr&, const RWDBExpr&)`	None. Default from the core library: `TRIM(BOTH expr FROM expr)`
`rwdbUpper(const RWDBExpr&)`	None. Corresponds to: `{fn UCASE(expr)}`