A library for parsing CodeBase (dBase) expressions and mechanically translating them into SQL expressions.

dBase	SQL	Notes
a + b * c	(a+(b*c))	Note correct operator precedence
(a + b) * c	((a+b)*c)	ditto
.T..AND..FALSE.	(TRUE AND FALSE)
"T"$L_NAME	CAST (STRPOS(RPAD(COALESCE("L_NAME", ''), 20, ' '),'T') AS bool)	Conversion from double quoted string to SQL's single quotes; $ to INSTR function call
(DATE() + 1) - STOD("20240731")	(( CURRENT_DATE +1)-TO_DATE('20240731','YYYYMMDD'))	Ugly, but deals with differences in Date representation

Running

cargo run will run the sample program (src/main.rs) which runs a bunch of test strings through the parse-translate-print cycle.

Design

• The parsing of dBase expressions is implemented with a handrolled lexer (src/lex.rs) and Pratt parser (src/parser.rs). The parser generally only needs to allocate once.
• The SQL AST is in src/translate.rs and the various SQL dialects are in src/translate.
• The SQL serialization is in src/to_sql.rs
• Limited support for evaluation of expressions is also provided in src/evaluate.rs