66 lines
1.5 KiB
Haskell
66 lines
1.5 KiB
Haskell
module ChuSQL.Syntax.AST (Statement (..), FromClause (..), Expr (..), SortDir (..), makeSelect) where
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import ChuSQL.Model (Column (..))
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-- 语法树：语句、数据来源、条件表达式、排序方向。
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-- * 语句
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-- | 一条语句：查 / 加 / 删 / 改 / 建表 / 删表
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data Statement
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= Select
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{ selectCols :: [String]
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, selectFrom :: FromClause
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, selectWhere :: Maybe Expr
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, selectOrderBy :: [(String, SortDir)]
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, selectLimit :: Maybe Int
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}
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| Insert String [String] [Expr]
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| Delete String (Maybe Expr)
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| Update String [(String, Expr)] (Maybe Expr)
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| CreateTable String [(String, Column)]
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| DropTable String
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deriving (Show, Eq)
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-- | 数据来源：单表，或两表拼接
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data FromClause
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= FromTable (Maybe String) String
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| FromJoin FromClause (Maybe String) String Expr
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deriving (Show, Eq)
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-- * 表达式
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-- | 条件表达式
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data Expr
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= Col String
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| LitInt Int
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| LitStr String
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| LitBool Bool
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| Gt Expr Expr
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| Lt Expr Expr
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| Eq Expr Expr
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| And Expr Expr
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| Or Expr Expr
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deriving (Show, Eq)
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-- * 排序
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-- | 排序方向
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data SortDir
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= Asc
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| Desc
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deriving (Show, Eq)
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-- * 构造
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-- | 造一个最简单的 SELECT
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makeSelect :: [String] -> String -> Maybe Expr -> Statement
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makeSelect cols tbl w =
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Select
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{ selectCols = cols
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, selectFrom = FromTable Nothing tbl
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, selectWhere = w
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, selectOrderBy = []
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, selectLimit = Nothing
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}
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