python學習--sql語句執行模擬工具

【作業內容】

        模擬sql執行過程，完成對特定表的增、刪、改、查。

【作業分析】

     隨着現在信息量的增加，以及數據庫提供的強大數據管理能力，數據庫編程編程了IT開發者必備的技能之一。數據庫開發者會預留數據庫對外接口，以便開發人員來使用，通過這些接口，我們可以執行我們的查詢、刪除、更行、插入等sql語句，而我們的作業內容則是為了更好的了解sql語句執行的過程，調高自己的sql語句編寫能力，也是想通過這個例子，對函數有進一步的了解，話不多少，代碼如下：

   

keyword_list = ['from','into','update']
spr = '      '

def SearchAll(strlist,table_name):
    '查詢'
    if 'where' in strlist:
        Condition_query(strlist,table_name)
    else:
        Query(strlist,table_name)

def Delete(strlist,table_name):
    '刪除數據項'
    temp_tablename = ''
    index = 0

    if 'where' not in strlist:
        index,colName = GetTableItemNum(table_name)
        f = open(table_name,'w')
        f.write(colName)
        f.close()
    else:
        temp_tablename = table_name + '_1'

        with open(temp_tablename,'a',encoding='utf8') as f1:
            with open(table_name,'r',encoding='utf8') as f:
                for line in f:
                    if not Judegfilter(strlist,line):
                        f1.write(line)
                    else:
                        index += 1

        os.remove(table_name)
        os.rename(temp_tablename,table_name)

    print("Delete %d item data." %index)

def Judegfilter(strlist,line):
    flag = False
    pos = strlist.index('where')
    colNameList = GetTableColName(strlist[pos - 1])
    line_list = list(str(line).strip('\n').split(spr))
    index = GetIndexInList(colNameList, strlist[pos + 1])
    colValue = strlist[pos + 3].strip('"').strip('\'')

    if '=' in strlist:
        if colValue == line_list[index + 1]:
            flag = True
    elif 'like' in strlist:
        if colValue in line_list[index + 1]:
            flag = True
    elif colValue.isdigit():
        if strlist[pos + 2] == '<':
            if int(colValue) > int(line_list[index + 1]):
                flag = True
        elif strlist[pos + 2] == '>':
            if int(colValue) < int(line_list[index + 1]):
                flag = True

    return flag

def GetTableItemNum(table_name):
    index = 0
    colName = ''

    with open(table_name,'r',encoding='utf8') as f:
        for line in f:

            if index == 0:
                colName = line.strip('\n')
            index += 1

    if index > 0:
        index -= 1

    return index,colName

def Update(sqlList,table_name):
    '更新數據項'
    pass

def Insert(sqlList,table_name):
    '插入數據項'
    index =  sqlList.index('into')
    '''
    因為sql語句中的方式為table(colname1,cloname2)，所以先取相應的值,然后將括號去掉，轉換成列表
    '''
    temp = sqlList[index +1].lower().strip(')')
    pos = str(temp).index('(')
    insertColName = temp[pos+1:len(temp)].split(',')

    if 'phone' not in insertColName:
        print('插入唯一鍵不存在，請檢查您的插入語句')
    else:
        temp = sqlList[index + 2].strip(')')
        insertValues = GetValueFromStr(temp)

        if len(insertValues) == 0:
            print('插入值不能為空，請檢查您的sql語句')
        else:
            InsertDataToDB(table_name, insertColName, insertValues)

def GetValueFromStr(temp):
    pos = str(temp).index('(')
    insertValues = temp[pos + 1:len(temp)].split(',')
    insertValues1 = []

    for line in insertValues:
        temp1 = line.strip('\'')
        insertValues1.append(temp1)

    return insertValues1

def InsertDataToDB(table_name, insertColName, insertValues):
    '插入數據到文件中'
    pos = insertColName.index('phone')
    value = insertColName[pos]
    flag = False

    pos = insertColName.index('phone')

    if pos > len(insertValues):
        print('插入值過少，請檢查您的sql語句')
    elif len(insertValues[pos]) == 0:
        print('插入值不能為空，請檢查您的sql語句')
    else:
        flag,tableColName = IsValueInDB(insertValues[pos], table_name)
        if flag:
            print("插入值已存在，請您檢查sql語句")
        else:
            WriteDataToDB(table_name, insertColName, insertValues,tableColName)

def IsValueInDB(value, table_name):
    '判斷插入值是否已經存在'
    index = 0
    templist = []
    flag = False

    with open(table_name,'r',encoding='utf8') as f:
        index = 0
        for line in f:
            if index == 0:
                templist = line.lower().strip(spr).split(spr)
            elif value in line:
                flag = True
                break

            index += 1

    return flag,templist

def WriteDataToDB(table_name, insertColName, insertValues,tableColName):
    '將數據組成合理的格式寫入到文件中'
    indexlist = []
    index = GetOrderIndex()
    temp = spr + str(index)
   # valuedir = GetValue

    '''
    with open(table_name, 'a',encoding='utf8') as f:
        for line in insertColName:
            pos = tableColName.index(line)
            indexlist.append(pos)
            lenNum = len(indexlist)
            temp = spr + str(index)

            if lenNum == 1:
                temp += pos * spr
            else:
                pos1 = indexlist[lenNum -1] - indexlist[lenNum -2]
                temp += pos1 * spr

            pos = insertColName.index(line)
            temp += insertValues[0]

            f.write(temp)
  '''

    PutOrderIndex(index +1)
    print("插入數據成功")

def GetOrderIndex():
    '獲取自增量最后值，該值存放在文件中'
    index = 0
    with open('index', 'r', encoding='utf8') as f:
        index = int(f.readline())

    return index

def PutOrderIndex(orderIndex):
    '將自增量寫入到文件中做記錄'
    with open('index', 'w', encoding='utf8') as f:
        temp = str(orderIndex)
        f.write(temp)

def Condition_query(strlist,table_name):
    '條件查詢:strlist(將sql語句拆分之后的列表)、strlist（表名）'
    colList = list(strlist[1].split(','))   #查詢項
    pos = GetIndexInList(strlist,'where')  #pos 條件判斷關鍵字位置
    index = 0
    total = -1

    with open(table_name, 'r', encoding='utf8') as f:
        for line in f:  #line文件中讀取信息
            temp = GetSearchvalue(line,strlist,index,colList,pos)
            index += 1

            if len(temp) != 0:
                print(temp)
                total += 1

            pass

    print('Total:', total)

def GetSearchvalue(line,strlist,index,colList,pos):
    'sql語句中的查詢條件中，條件項為數字類型'
    temp = ''
    if index == 0:
        temp = Print_colname(strlist, colList,line)
    else:
        temp = CheckCondition(strlist,line,pos)
        pass

    return temp

def Print_colname(strlist,colList,line):
    temp = ''
    line = line.strip('\n')
    if '*' in strlist:
        temp = line
    else:
        for colIndex in colList:
            temp += colIndex
            temp += spr

    return temp

def CheckCondition(strlist, line, pos):
    '判斷當前值是否符合查詢條件過濾值'
    temp = ''
    colNameList = GetTableColName(strlist[pos - 1])
    line_list = list(str(line).strip('\n').split(spr))
    index = GetIndexInList(colNameList,strlist[pos+1])
    colValue = strlist[pos + 3].strip('"').strip('\'')

    if '=' in strlist:
        if colValue == line_list[index + 1]:
            temp = GetDataFromLine(line_list, line, strlist,pos)
    elif 'like' in strlist:
        if colValue in line_list[index + 1]:
            temp = GetDataFromLine(line_list, line, strlist, pos)
    elif colValue.isdigit():
        if strlist[pos + 2] == '<':
            if int(colValue) > int(line_list[index + 1]):
                temp = GetDataFromLine(line_list, line, strlist,pos)
        elif strlist[pos + 2] == '>':
            if int(colValue) < int(line_list[index + 1]):
                temp = GetDataFromLine(line_list, line, strlist,pos)

    return temp

def GetDataFromLine(line_list, line, strlist,pos):
    '將符合條件的數據進行分揀，依據查詢的字段名來取相應的值,如果是全字段，則直接返回值'
    temp = ''

    if '*' in strlist:
        temp = line.strip('\n')
    else:
        selColIndex = list(strlist[1].split(','))
        colNameList = GetTableColName(strlist[pos-1])
        selColIndexlist = GetIndexWithColName(selColIndex,colNameList)
        for data in selColIndexlist:
            temp += line_list[data+1].strip('\n')
            temp += spr

    return temp

def Query(strlist,table_name):
    '非條件查詢'
    index = 0

    if '*' in strlist:
        with open(table_name, 'r', encoding='utf8') as f:
            for line in f:
                print(line.strip('\n'))
                index += 1
    else:
        index = Query_someone(strlist,table_name)

    print("Total:%d" %(index-1))

def Query_someone(strlist,table_name):
    '查詢任一一項或者多項數據'
    colList = list(strlist[1].split(','))
    colnameList = GetTableColName(table_name)
    colNameIndex = GetIndexWithColName(colList,colnameList)

    '''
    1、讀取文件中第一行數據，獲得字段信息，判斷要查詢的字段是否為文件字段項，如果不是，
        提示查詢出錯；
    2、獲取查詢字段在文件字段項中的位置。獲取該位置，在之后讀取文件中的數據時使用到
    '''
    if len(colNameIndex) == 0:
        print('【Error】查詢字段不存在')
        return 0
    else:
        colNameIndex.sort()
        index = 0
        with open(table_name, 'r', encoding='utf8') as f:
            for line1 in f:
                strInfo = GetColValue(line1, colNameIndex, index)
                index += 1
                print(strInfo)

        return index

def GetTableColName(table_name):
    '獲取表中字段項列表'
    colnameList = []
    with open(table_name, 'r', encoding='utf8') as f:
        colnameList = list(f.readline().lower().strip('\n').split(spr))

    return colnameList

def GetTableName(strSql):
    '通過sql語句轉化之后的列表，獲取到表名'
    name = ''
    list = strSql.split(' ')

    for line in keyword_list:
        if line in list:

            name_pos = list.index(line)
            if len(list) == name_pos+1:
                break
            elif line == 'into':
                temp = list[name_pos+1]
                name = SperString(temp,'(')
            else:
                name = list[name_pos+1]

            break

    return name

def SperString(strData, sper):
    temp = ''

    if sper in strData:
        pos = strData.index(sper)
        temp = strData[0:pos]
    else:
        temp = strData

    return temp

def GetIndexInList(list, name):
    '通過列表中的數據項，獲取數據項在列表中的位置信息'
    if name in list:
        return list.index(name)
    else:
        return -1

def GetIndexWithColName(colList, colnameList = []):
    '查詢時會遇到查詢多項數據，此處是將每個數據項在表中對應的位置信息獲取到'
    colNameIndex = []
    for line in colList:
        if line.lower() in colnameList:
            index = colnameList.index(line.lower())
            colNameIndex.append(index)

    return colNameIndex

def GetColValue(colValue,list,index):
    '通過表中數據項所在位置，取出相應的值'
    strInfo = ''

    for line2 in list:
        templist = colValue.split(spr)
        if index == 0:
            strInfo += templist[line2].strip('\n')
        else:
            strInfo += templist[line2 + 1].strip('\n')
        strInfo += spr

    return strInfo

def RunSql(strSql):
    '執行sql語句'
    sqlList = strSql.strip('\n').split(' ')
    table_name = GetTableName(strSql)
    oper = sqlList[0].lower()

    flag,errorInfo = JudgeSqlIsTrue(sqlList,table_name)
    if flag:
        First_Keyword_list[oper](sqlList,table_name)
    else:
        print('執行的sql語句有語法錯誤,錯誤提示：【%s】。請檢查您的執行語句' %errorInfo)

def JudgeSqlIsTrue(strSqlList,table_Name):
    '判斷執行語句是否符合語法負責'
    flag = False
    temp = ''

    if len(strSqlList) == 0:
        print('空語句無法執行')
    else:
        if strSqlList[0].lower() not in First_Keyword_list:
            temp = '執行語句不符合執行規則，沒有找到執行關鍵字'
        elif not JudgeTableName(table_Name):
            temp = '查詢的表不存在'
        elif not JudgeColName(strSqlList, table_Name):
            temp = '查詢的表字段不存在'
        else:
            flag = True

    return flag,temp

def JudgeTableName(table_Name):
    isExists = os.path.exists(table_Name)

    return isExists

def JudgeColName(strSqlList,table_Name):
    '判斷操作字段是否在表中'
    if 'delete'in strSqlList or '*' in strSqlList:
        return True
    else:
        searchColNamelist = GetSearchNameFromSql(strSqlList)
        tablecolNamelist = GetTableColName(table_Name)

        if len(searchColNamelist) == 0:
            return False

        for line in searchColNamelist:
            if line not in tablecolNamelist:
                return False

    return True

def GetSearchNameFromSql(strSqlList):
    '從sql語句中提取字段名'
    tempList = []

    if 'select' in strSqlList:
        tempList = strSqlList[1].lower().split(',')
    elif 'insert' in strSqlList:
        temp = strSqlList[2].lower().strip(')')

        if '(' in temp:
            pos = temp.index('(')
            tempList = (temp[pos+1:len(temp)]).split(',')
            print(tempList)
    elif 'update' in strSqlList:
        pass

    return tempList

#strSql = 'select * from staff_table where age > 22'
#select * from staff_table where name like '龍龍'
#insert into staff_table(name,dept) values('龍龍','教師')

import os
time = 0
First_Keyword_list = {'select':SearchAll,'insert':Insert,'update':Update,'delete':Delete}

while time < 3:
    strSql = input('sql>')
    RunSql(strSql)
    time += 1