# FiveSql2 — SQL Engine for Harbour DBF/NTX/CDX

**Pratt parser + SQL:1992-2023 full standard support**
**Supports both NTX (Clipper) and CDX (FoxPro/ADS) indexes**

## Architecture

```
five_SQL("SELECT ...")
   │
   ├── TSqlLexer        Tokenizer
   ├── TSqlParser2      Pratt parser (data-driven operators)
   ├── TSqlExecutor     Query executor (Volcano model)
   │     ├── TSqlAlias  Central alias manager (no collisions)
   │     ├── TSqlIndex  NTX/CDX index optimization (auto-detect)
   │     ├── TSqlAgg    GROUP BY / aggregation
   │     ├── TSqlSort   ORDER BY / DISTINCT
   │     ├── TSqlDDL    CREATE/DROP/ALTER TABLE/INDEX
   │     └── TSqlTxn    BEGIN/COMMIT/ROLLBACK
   ├── TSqlExpr         AST nodes + expression evaluation
   └── TSqlFunc         60+ scalar functions
```

## Build & Test

```bash
export PATH="/path/to/harbour-core/bin/linux/gcc:$PATH"
export HB_INSTALL_PREFIX="/path/to/harbour-core"

make          # Build all tests
make test     # Run all 157 tests
make bench    # Parser benchmark
make clean    # Clean
```

## SQL Standard Coverage

| Standard   | Features | Tests |
|------------|----------|:-----:|
| SQL:1992   | SELECT, JOIN, GROUP BY, HAVING, Subquery, CASE, CAST | 43 |
| SQL:1999   | CTE, Recursive CTE, Window Functions, MERGE | 10 |
| SQL:2003   | SIMILAR TO, GROUPING SETS, LATERAL, Window frames | 64 |
| SQL:2008   | FETCH/OFFSET, FOR UPDATE, Extended MERGE | (incl.) |
| SQL:2016   | JSON functions, LISTAGG | (incl.) |
| SQL:2023   | ANY_VALUE, GREATEST/LEAST, BOOL_AND/OR | (incl.) |
| Challenge  | LeetCode-level complex queries | 15 |
| Extreme    | Production analytics stress tests | 15 |

## Adding New Operators

Edit `TSqlParser2.prg`, method `InitInfixTables()`:

```prg
::hInfixTT[ TK_MYOP ] := { "<=>", 40, 41, ND_BIN }
```

One line. No structural changes needed.

## Copyright

Copyright (c) 2025-2026 Charles KWON (Charles KWON OhJun)
Email: charleskwonohjun@gmail.com
All rights reserved.