生成的SQL查询不会返回与sqlite3 HDBC中相应的静态查询相同的内容

Question

我在Haskell中生成SQL查询并使用HDBC将它们提交到SQLite(3)数据库.现在,此函数返回一个查询:

import Database.HDBC.Sqlite3 
import Database.HDBC
data UmeQuery = UmeQuery String [SqlValue] deriving Show

tRunUmeQuery :: UmeQuery -> FilePath -> IO [[SqlValue]]
tRunUmeQuery (UmeQuery q args) dbFile = do
    conn <- connectSqlite3 dbFile
    stat <- prepare conn q
    s <- execute stat args
    res <- fetchAllRows' stat 
    disconnect conn
    return $ res

selectPos targetlt parentlt op pos = let 
    q= "select TARGET.* from levels tl, labeltypes tlt, segments TARGET, 
    (select TARGET.session_id session_id,SECONDARY.labeltype_id labeltype_id, 
    SECONDARY.label_id label_id,min(TARGET.label_id) min_childlabel_id from 
    levels tl, labeltypes tlt, segments TARGET, segments SECONDARY, labeltypes slt, 
    levels sl where TARGET.session_id = SECONDARY.session_id and ((SECONDARY.start 
    <= TARGET.start and TARGET.end <= SECONDARY.end) or (TARGET.start <= SECONDARY.start 
    and SECONDARY.end <= TARGET.end)) and tl.name = ? and sl.name = ? and SECONDARY.label '
    != '' and tl.id = tlt.level_id and sl.id = slt.level_id and tlt.id = TARGET.labeltype_id 
    and slt.id = SECONDARY.labeltype_id group by TARGET.session_id, TARGET.labeltype_id, 
    SECONDARY.label_id) SUMMARY, segments SECONDARY, labeltypes slt, levels sl where 
    TARGET.session_id = SECONDARY.session_id and TARGET.session_id = SUMMARY.session_id 
    and ((SECONDARY.start <= TARGET.start and TARGET.end <= SECONDARY.end) or (TARGET.start 
    <= SECONDARY.start and SECONDARY.end <= TARGET.end)) and tl.name = ? and sl.name = ? 
    and tl.id = tlt.level_id and tlt.id = TARGET.labeltype_id and SUMMARY.labeltype_id = 
    SECONDARY.labeltype_id and SUMMARY.label_id = SECONDARY.label_id and sl.id = slt.level_id 
    and slt.id = SECONDARY.labeltype_id and (TARGET.label_id - SUMMARY.min_childlabel_id +1) = 2 "
    a = [toSql targetlt, toSql parentlt, toSql targetlt, toSql parentlt ]
    in UmeQuery q a

当应用于数据库时返回正确的东西:

> let a =selectPos "Word" "Utterance" "=" 2
> let b = tRunUmeQuery a testdb 
> b

产出:

[[SqlByteString"1",SqlByteString"2",SqlByteString"3",SqlByteString"0.149383838383838",SqlByteString"0.312777777777778",SqlByteString"second"],[SqlByteString"1",SqlByteString"2",SqlByteString"6",SqlByteString "0.507488888888889",SqlByteString"0.655905050505051",SqlByteString"第四",[SqlByteString"2",SqlByteString"2",SqlByteString"3",SqlByteString"0.149383838383838",SqlByteString"0.312777777777778",SqlByteString"second"],[SqlByteString" 2",SqlByteString"2",SqlByteString"6",SqlByteString"0.507488888888889",SqlByteString"0.655905050505051",SqlByteString"第四",[SqlByteString"3",SqlByteString"2",SqlByteString"3",SqlByteString"0.149383838383838", SqlByteString"0.312777777777778",SqlByteString"second"],[SqlByteString"3",SqlByteString"2",SqlByteString"6",SqlByteString"0.507488888888889",SqlByteString"0.655905050505051",SqlByteString"4th"]]

现在,当我需要在查询中插入几个小的动态部分时,就像这样(抱歉,你必须滚动到字符串的末尾才能看到这个):

selectPos targetlt parentlt op pos = let
    q= "select TARGET.* from levels tl, labeltypes tlt, segments TARGET, 
    (select TARGET.session_id session_id,SECONDARY.labeltype_id labeltype_id,
    SECONDARY.label_id label_id,min(TARGET.label_id) min_childlabel_id from 
    levels tl, labeltypes tlt, segments TARGET, segments SECONDARY, labeltypes slt,
     levels sl where TARGET.session_id = SECONDARY.session_id and ((SECONDARY.start 
     <= TARGET.start and TARGET.end <= SECONDARY.end) or (TARGET.start <= SECONDARY.start 
     and SECONDARY.end <= TARGET.end)) and tl.name = ? and sl.name = ? and SECONDARY.label 
     != '' and tl.id = tlt.level_id and sl.id = slt.level_id and tlt.id = TARGET.labeltype_id 
     and slt.id = SECONDARY.labeltype_id group by TARGET.session_id, TARGET.labeltype_id, 
     SECONDARY.label_id) SUMMARY, segments SECONDARY, labeltypes slt, levels sl where 
     TARGET.session_id = SECONDARY.session_id and TARGET.session_id = SUMMARY.session_id 
     and ((SECONDARY.start <= TARGET.start and TARGET.end <= SECONDARY.end) or (TARGET.start
      <= SECONDARY.start and SECONDARY.end <= TARGET.end)) and tl.name = ? and sl.name = ? 
      and tl.id = tlt.level_id and tlt.id = TARGET.labeltype_id and SUMMARY.labeltype_id = 
      SECONDARY.labeltype_id and SUMMARY.label_id = SECONDARY.label_id and sl.id = slt.level_id 
      and slt.id = SECONDARY.labeltype_id and (TARGET.label_id - SUMMARY.min_childlabel_id +1) " 
      ++ op ++ " ? "
    a = [toSql targetlt, toSql parentlt, toSql targetlt, toSql parentlt , toSql pos]
    in UmeQuery q a

并做同样的事情,我得到:

> let a =selectPos "Word" "Utterance" "=" 2
> let b = tRunUmeQuery a testdb  
> b 

[]

为什么第二个查询没有返回任何东西(或者实际上是同一个东西)？

有任何想法吗？

编辑:

我进一步调查了这一点,认为这可能与懒惰有某种关系.好了,现在已经重塑了这个:

selectPos :: String -> String -> String -> Integer -> [[SqlValue]]
selectPos targetlt parentlt op pos = let
    q= foldl' (++)  [] ["select TARGET.* from levels tl, labeltypes tlt, segments TARGET, 
    (select TARGET.session_id session_id,SECONDARY.labeltype_id labeltype_id,SECONDARY.label_id 
    label_id,min(TARGET.label_id) min_childlabel_id from levels tl, labeltypes tlt, segments 
    TARGET, segments SECONDARY, labeltypes slt, levels sl where TARGET.session_id = SECONDARY.session_id "
    ,matchstring , " and tl.name = ? and sl.name = ? and SECONDARY.label != '' and tl.id = tlt.level_id 
    and sl.id = slt.level_id and tlt.id = TARGET.labeltype_id and slt.id = SECONDARY.labeltype_id 
    group by TARGET.session_id, TARGET.labeltype_id, SECONDARY.label_id) SUMMARY, segments SECONDARY, 
    labeltypes slt, levels sl where TARGET.session_id = SECONDARY.session_id and TARGET.session_id = 
    SUMMARY.session_id " , matchstring , " and tl.name = ? and sl.name = ? and tl.id = tlt.level_id 
    and tlt.id = TARGET.labeltype_id and SUMMARY.labeltype_id = SECONDARY.labeltype_id and SUMMARY.label_id
     = SECONDARY.label_id and sl.id = slt.level_id and slt.id = SECONDARY.labeltype_id and 
     (TARGET.label_id - SUMMARY.min_childlabel_id +1) " , op , " ? "]  
    a = [toSql targetlt, toSql parentlt, toSql targetlt, toSql parentlt , toSql (pos :: Integer)]
    in UmeQuery q a

不幸的是,这对问题没有帮助(当我:在ghci中sprint函数的返回值时,它仍然没有评估).所以,懒惰可能是某种方式的问题,但我不知道如何使这充分评估..？请问,有什么想法吗？

Answer 1

所以...只是陈述事实：

• 你的代码确实运行它不会产生任何语法错误或警告（这适用于 haskell 和 haskell 运行的 sql）
• 原始查询确实运行，但未添加 op 和 pos （其中已经有动态部分）
• 你得到一个空集（意味着查询不返回任何行）...

如果所有这些都是真的，那么我就会相信查询一定是有效的，但却是错误的。检查数据？转储查询，手动运行它。让我知道。

要尝试的事情：

• 尝试回滚更改以查看它是否仍然有效（这样您就知道没有任何内容被意外更改并验证数据是否相同）。
• 您可以尝试使用更简单的查询进行测试吗？
• 您可以尝试转储查询变量并在数据库中手动运行它（无论有没有更改）？
• 您是否想发布几行数据（某些行将返回，某些行不会），以便我可以将其加载到临时表测试中？
• 尝试仅添加pos到工作查询（使用op硬编码）并查看是否有效
• 尝试仅添加op到工作查询（使用pos硬编码）并查看是否有效
• 确保您在各处都以正确的顺序列出变量

出于某种原因，我一直认为这可能是转换或其他问题的数据类型问题，但我从未使用过 Haskell，所以我无法真正猜测还会发生什么。

其他建议：

• 正确格式化您的查询，使其易于阅读（至少一点点，所以它不是一个巨大的字符串）
• 更新您的问题以包括有关如何设置您的环境的规范（以及软件/事物和其他内容的版本）
• 如果您认为问题与懒惰有关，请尝试强制评估......？但查询确实已经具有动态/可变部分。我必须假设他们会遇到同样的问题，如果是这种情况，并且查询一开始就无法工作。
• 这很愚蠢，但你并没有碰巧改变你从中提取的数据库，不是吗？

sqlite> select * from temp;
temp_id     temp_name
----------  ----------
1           one
2           two
3           three

import Database.HDBC.Sqlite3 
import Database.HDBC

testdb = "C:\\Users\\Kim!\\test.db"

data UmeQuery = UmeQuery String [SqlValue] deriving Show

tRunUmeQuery :: UmeQuery -> FilePath -> IO [[SqlValue]]

tRunUmeQuery (UmeQuery q args) dbFile = do
    conn <- connectSqlite3 dbFile
    stat <- prepare conn q
    s <- execute stat args
    res <- fetchAllRows' stat 
    disconnect conn
    return $ res
     
selectPos temp_id op = let 
   q = "select temp_id, temp_name from temp where temp_id = " ++ op ++ " ?";  
   a = [ toSql temp_id ] 
   in UmeQuery q a

> let a = selectPos (1::Int) "="
> let b = tRunUmeQuery a testdb 
> b
[[SqlByteString "1",SqlByteString "one"]]

> let a = selectPos (1::Int) ">"
> let b = tRunUmeQuery a testdb 
> b
[[SqlByteString "2",SqlByteString "two"],[SqlByteString "3",SqlByteString "three"]] 

快速说明：今天之前我从未接触过 Haskell 或 SQLite。我正在 Windows 7 Professional 64 位上使用 SQLite3 - sqlite-dll-win64-x64-201409301904.zip运行 Haskell Platform 2014.2.0.0 。

编辑：这也有效...（查询也有一点不同）

import Data.List

selectPos temp_id op temp_name = let 
   q = foldl' (++)  [] [
       "select temp_id, temp_name        " ++ 
       "from   temp                      " ++
       "where  temp_id " , op , " ? or   " ++
       "       temp_name = ?             "]
   a = [ toSql (temp_id::Int), toSql temp_name ]  
   in UmeQuery q a

> let a = selectPos 1 ">" "one"
> let b = tRunUmeQuery a testdb 
> b
[[SqlByteString "1",SqlByteString "one"],[SqlByteString "2",SqlByteString "two"],[SqlByteString "3",SqlByteString "three"]] 

编辑：这有效......

sqlite> insert into temp values (4, "Word"); 
sqlite> insert into temp values (5, "Utterance");

selectPos targetlt parentlt op pos = let 
   q = " select temp_id, temp_name        \
       \ from   temp                      \
       \ where  temp_name = ?  or         \
       \        temp_name = ?  or         \
       \        temp_name = ?  or         \
       \        temp_name = ?  or         \
       \        temp_id "++op++" ?        "
   a = [toSql targetlt, toSql parentlt, 
        toSql targetlt, toSql parentlt, 
        toSql (pos::Int) ]
   in UmeQuery q a

> let a = selectPos "Word" "Utterance" "=" 2
> let b = tRunUmeQuery a testdb 
> b
[[SqlByteString "2",SqlByteString "two"],[SqlByteString "4",SqlByteString "Word"],[SqlByteString "5",SqlByteString "Utterance"]]

所以...在您在问题中发布的查询中...也存在意想不到的差异...这与变量无关。这是一个单引号。不确定是否只是复制和粘贴中的拼写错误或什么。我显然无法运行您的查询，因为这正是因为需要提供大量的模拟表和数据......

编辑：哈...我又回到了这个问题。selectPos我注意到你在最后一个示例上方有一行我没有使用的额外行。我必须这样做才能让它工作......[[SqlValue]]或者IO [[SqlValue]]因为最后一个值对我不起作用；错误（我只是在尝试，我不知道这些值是否真正有意义）。

selectPos :: String -> String -> String -> Integer -> UmeQuery
selectPos targetlt parentlt op pos = let 
   q = " select temp_id, temp_name        \
       \ from   temp                      \
       \ where  temp_name = ?  or         \
       \        temp_name = ?  or         \
       \        temp_name = ?  or         \
       \        temp_name != ?  or        \
       \        temp_id "++op++" ?        "
   a = [toSql targetlt, toSql parentlt, 
        toSql targetlt, toSql parentlt, 
        toSql pos ]
   in UmeQuery q a

> let a = selectPos "Word" "Utterance" "=" 2
> let b = tRunUmeQuery a testdb 
> b
[[SqlByteString "1",SqlByteString "one"],[SqlByteString "2",SqlByteString "two"],[SqlByteString "3",SqlByteString "three"],[SqlByteString "4",SqlByteString "Word"],[SqlByteString "5",SqlByteString "Utterance"]] 

不管怎样...我很高兴今天能编写我的第一个 Haskell 程序...！