Question

我有以下数据表：

Name              Expression
FirstName           NULL
LastName            NULL
FullName          CONCAT(FirstName,LastName)
Gender              NULL
FullNameWGender   CONCAT(FullName,Gender)

如何使用SQL语句生成从表中获取的以下数据：

FirstName, LastName, CONCAT(FirstName,LastName) AS FullName, Gender, CONCAT(CONCAT(FirstName,LastName),Gender) AS FullNameWGender

我正在使用MySQL。

我不希望完整的代码，但至少是一个起点，因为我不知道如何确保一旦我到达具有CONCAT的表达式列中的数据并处理它。

与上面的例子类似，在表中它是CONCAT(FullName,...)。但是使用我的SQL，我必须提取并处理它以显示为CONCAT(CONCAT(FirstName,LastName),....) ...

任何帮助都会很棒！

Answer 1

您可以为FullNameWGender做些什么是CONCAT（FirstName，LastName，Gender）。

Select FirstName, LastName, CONCAT(FirstName,LastName) AS FullName, Gender, CONCAT(FirstName, LastName,Gender) AS FullNameWGender

CONCAT可用于两个以上的字符串。 dev.mysql.com

Answer 2

好吧，我有游标形式的代码（我别无选择）

使用与上面相同的表但有更多数据：

ID    NAME                      EXPRESSION
1      FirstName,                   NULL
2      LastName,                    NULL
3      FullName,                  CONCAT( FirstName, LastName)
4      Gender,                      NULL
5      FullNameWGender,           CONCAT( FullName, Gender)
6      Income,                      NULL
7      Expense,                     NULL
8      Savings,                   ( Income,- Savings,)
9      FullNameWSavings,          CONCAT( FullName, Savings,)
10     Month,                       NULL
11     FullNameWSavingsByMonth,   CONCAT( FullNameWSavings, Month,)

获取更新的表格如下：

ID    Name                      Expression
1      FirstName,                   NULL
2      LastName,                    NULL
3      FullName,                  CONCAT( FirstName, LastName)
4      Gender,                      NULL
5      FullNameWGender,           CONCAT(CONCAT( FirstName, LastName) Gender)
6      Income,                      NULL
7      Expense,                     NULL
8      Savings,                   ( Income,- Savings,)
9      FullNameWSavings,          CONCAT(CONCAT( FirstName, LastName)( Income,-    Savings,))
10     Month,                       NULL
11     FullNameWSavingsByMonth,   CONCAT(CONCAT(CONCAT( FirstName, LastName)( Income,- Savings,)) Month,)

仅供任何人参考（希望它可以提供帮助（非常感谢@Nappa The Saiyan的答案），以下是代码：

DECLARE @id_name INT
DECLARE @id_expression INT
DECLARE @expression NVARCHAR (MAX)
DECLARE @cutExpression NVARCHAR (100)
DECLARE @name NVARCHAR (100)
DECLARE @newExpression NVARCHAR (MAX)
DECLARE @temp NVARCHAR (MAX)

DECLARE @rowNumExp INT
DECLARE @rowNumName INT
DECLARE @rowNum INT
SET @rowNum = 0
SET @rowNumExp = 0
SET @rowNumName = 0

DECLARE expressionList CURSOR FOR
SELECT ID, EXPRESSION FROM table1
OPEN expressionList
FETCH NEXT FROM expressionList
    INTO @id_expression, @expression

WHILE @@FETCH_STATUS = 0
BEGIN
    SET @rowNumExp = @rowNumExp + 1
        IF (@expression IS NOT NULL)
        BEGIN
            DECLARE nameList CURSOR FOR
            SELET ID, NAME FROM table1
            OPEN nameList
            FETCH NEXT FROM nameList
                INTO @id_name, @name

            WHILE @@FETCH_STATUS = 0
            BEGIN
                IF(CHARINDEX(@name,@expression)>0)
                BEGIN
                    SET @cutExpression = SUBSTRING(@expression,
                                                   CHARINDEX(@name,@expression),
                                                   LEN(@name))
                    SET @temp = (SELECT EXPRESSION FROM table1 WHERE ID = @id_name)
                    IF(@temp IS NOT NULL)
                    BEGIN
                        SET @newExpression = REPLACE (@expression, @name, @temp)
                        UPDATE table1
                            SET EXPRESSION = @newExpression
                            WHERE ID = @id_expression
                        SET @expression = @newExpression

                        CLOSE nameList
                        DEALLOCATE nameList

                        DECLARE nameList CURSOR FOR
                        SELECT ID, NAME FROM table1
                        OPEN nameList
                        FETCH NEXT FROM nameList
                            INTO @id_name, @name
                    END
                END
                SET @rowNumName = @rowNumName + 1
                FETCH NEXT FROM nameList
                    INTO @id_name, @name
            END
            CLOSE nameList
            DEALLOCATE nameList
        END
        FETCH NEXT FROM expressionList
            INTO @id_expression, @expression
END
CLOSE expressionList
DEALLOCATE expressionList

限制：

Name列的起始字符必须是空格
Name列的最后一个字符必须是'，'Eg在name列中：“ FirstName，“而不是”FirstName，“
表达式中的所有名称后面都必须跟一个“，”例如在表达式列中： “CONCAT（FullName，Savings，）”而非“CONCAT（FullName，Savings）”

无论Expression中可用的“Name”的数量是什么，它没有NULL作为自己的表达式，该东西会将所有内容格式化为上面的第二个表。

SQL脚本从存储的描述中生成查询

2 个答案: