如何将两个 sql 查询合并为一个查询

Question

我正在为我的程序编写自定义脚本：

// You might want to use a date range and specify the first Sunday and use that variable.
// Or, you may want to have a user request variable where they key in the starting Sunday #YYYY MM DD#

// Let us work out the current week number
$iStartWeekNumber = $Today#CUSTOMDATE[%W] + 1
TEXT "Current week number (1 to 52): $iStartWeekNumber"
EOL

// Let us work out the current year
$iThisYear = $Today#CUSTOMDATE[%Y]
TEXT "Current year: $iThisYear"
EOL

// Now we can do a manual for loop from iStartWeekNumber to the end of the year
TEXT "TODO: Work out how to show the date nicely formatted"
EOL
$datWeek = $Today
LOOP AS $iWeekNumber FROM $iStartWeekNumber TO 52
    $datWeek = $datWeek + 7
    TEXT "Week: $iWeekNumber"
    EOL
    TEXT "Date: {$datWeek#SHORTDATE}"
    EOL

    // Iterate all available speakers
    LOOP FROM "Congregation Speakers" NODATERANGE WHERE "Congregation" IS "$LocalCong" AND "notavail" IS "0"  SORTBY "Speaker"

        // Requirement 1
        // 1. He is not in program for a talk in our home or another congregation for that same WEEKEND (either saturday or sunday)

        // Store the current speaker into a variable
        VARIABLE_FIELD "Speaker" "$strCurrentSpeaker"

        LOOP SQL "SELECT * FROM [Home Talks] WHERE ((DatePart('ww',[Last Given],2)=$iWeekNumber)) AND ((DatePart('yyyy',[Last Given])=$iThisYear)) AND [Speaker] = '$strCurrentSpeaker' AND [Congregation]='$LocalCong'" ROW_COUNT "$iNumHomeTalks"
        END_LOOP

        LOOP SQL "SELECT * FROM [Away Talks] WHERE ((DatePart('ww',[Talk Date],2)=$iWeekNumber)) AND ((DatePart('yyyy',[Talk Date])=$iThisYear)) AND [Brother] = '$strCurrentSpeaker'" ROW_COUNT "$iNumAwayTalks"
        END_LOOP

        IF "$iNumHomeTalks" IS "0" AND "$iNumAwayTalks" IS "0"
            // Requirement 2
            // 2. He should not give a talk more than once in a MONTH (so he is unavailable if he will be giving a talk during the month)
            $iMonth = date_part($datWeek,"M")
            LOOP SQL "SELECT * FROM [Home Talks] WHERE ((DatePart('m',[Last Given])=$iMonth)) AND ((DatePart('yyyy',[Last Given])=$iThisYear)) AND [Speaker] = '$strCurrentSpeaker' AND [Congregation]='$LocalCong'" ROW_COUNT "$iNumHomeTalksForMonth"
            END_LOOP
            LOOP SQL "SELECT * FROM [Away Talks] WHERE ((DatePart('m',[Talk Date])=$iMonth)) AND ((DatePart('yyyy',[Talk Date])=$iThisYear)) AND [Brother] = '$strCurrentSpeaker'" ROW_COUNT "$iNumAwayTalksForMonth"
            END_LOOP
            $iTotalTalksForMonth = $iNumHomeTalksForMonth + $iNumAwayTalksForMonth
            IF "$iTotalTalksForMonth" IS "0"
                // Requirement 3
                // 3. That same weekend either one or more than x speakers are not out for a talk or unavailable

                // TO DO
                TEXT "$strCurrentSpeaker"
                EOL
            END_IF
        END_IF
    END_LOOP

    BLANK *1
END_LOOP

我想特别提请您注意两组 SQL 查询:

第 1 组：

LOOP SQL "SELECT * FROM [Home Talks] WHERE ((DatePart('ww',[Last Given],2)=$iWeekNumber)) AND ((DatePart('yyyy',[Last Given])=$iThisYear)) AND [Speaker] = '$strCurrentSpeaker' AND [Congregation]='$LocalCong'" ROW_COUNT "$iNumHomeTalks"
END_LOOP
LOOP SQL "SELECT * FROM [Away Talks] WHERE ((DatePart('ww',[Talk Date],2)=$iWeekNumber)) AND ((DatePart('yyyy',[Talk Date])=$iThisYear)) AND [Brother] = '$strCurrentSpeaker'" ROW_COUNT "$iNumAwayTalks"
END_LOOP

并设置 2：

LOOP SQL "SELECT * FROM [Home Talks] WHERE ((DatePart('m',[Last Given])=$iMonth)) AND ((DatePart('yyyy',[Last Given])=$iThisYear)) AND [Speaker] = '$strCurrentSpeaker' AND [Congregation]='$LocalCong'" ROW_COUNT "$iNumHomeTalksForMonth"
END_LOOP
LOOP SQL "SELECT * FROM [Away Talks] WHERE ((DatePart('m',[Talk Date])=$iMonth)) AND ((DatePart('yyyy',[Talk Date])=$iThisYear)) AND [Brother] = '$strCurrentSpeaker'" ROW_COUNT "$iNumAwayTalksForMonth"
END_LOOP

以上是我自己的脚本语言。但在幕后，它采用原始 SQL 查询并使用 Jet 在 Microsoft Access 数据库上运行它。

它们工作正常。但是我想知道是否可以将两组查询合并为一组？如您所见，我要确定的只是找到的记录数。因此，如果我可以组合 [Home Talks] 和 [Away Talks] 的查询，我最终只会执行 2 个查询，而不是四个。

在我看来我需要使用 UNION 但其中一个字段在每个字段中都不同 table:

Last Given
Talk Date

所以我不能只在两个查询之间拼接关键字 UNION。

Answer 1

您可以通过为字段名称添加别名来使用 UNION：

SELECT [Last Given] AS MyFieldName FROM [Home Talks]
UNION
SELECT [Talk Date] AS MyFieldName FROM [Away Talks]

您只需列出单个字段而不是 *，并确保任何输出字段匹配类型（或转换为字符串作为查询的一部分）和名称（别名）。

编辑：如果两个字段完全不相关（相对于具有不同字段名称的相同或相似信息），这是一个附加选项：

SELECT [Last Given], NULL AS [Talk Date] FROM [Home Talks]
UNION
SELECT NULL AS [Last Given], [Talk Date] FROM [Away Talks]

如何将两个 sql 查询合并为一个查询

How to take two sql queries and combine them into a single query

ms-access

jet