完成Haskell部分的SQL词法分析器

chusql-engine/app/Main.hs

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+module Main where
+
+import ChuSQL.Eval.Executor
+import ChuSQL.Model
+import ChuSQL.Syntax.Ast
+import ChuSQL.Syntax.Parser
+
+users :: Table
+users =
+    Table
+        { tableName = "users"
+        , tableCols = ["name", "age"]
+        , tableRows =
+            [ [("name", VStr "Alice"), ("age", VInt 25)]
+            , [("name", VStr "Bob"), ("age", VInt 17)]
+            , [("name", VStr "Carol"), ("age", VInt 30)]
+            ]
+        }
+
+db :: Database
+db = [("users", users)]
+
+-- runQuery 返回 (更新后的数据库, 结果行)；演示只关心结果行
+rowsOf :: Either String (Database, [Row]) -> Either String [Row]
+rowsOf = fmap snd
+
+main :: IO ()
+main = do
+    let q1 = makeSelect ["name"] "users" (Just (Gt (Col "age") (LitInt 18)))
+    print (rowsOf (runQuery db q1))
+
+    let q2 = makeSelect ["*"] "users" Nothing
+    print (rowsOf (runQuery db q2))
+
+    let q3 = makeSelect ["name"] "nonexistent" Nothing
+    print (rowsOf (runQuery db q3))
+
+    let q4 =
+            makeSelect
+                ["name"]
+                "users"
+                ( Just
+                    ( Or
+                        (Lt (Col "age") (LitInt 18))
+                        (Gt (Col "age") (LitInt 30))
+                    )
+                )
+    print (rowsOf (runQuery db q4))
+
+    -- 解析 SQL 文本，再交给执行引擎
+    let parsed = parseQuery "SELECT name FROM users WHERE age > 18 AND name = 'Alice'"
+    print (rowsOf (parsed >>= runQuery db))