将数据从一个表数据插入到另一个表

Question

我有两张桌子TAB1 和TAB2。我想在特定列的TAB2 中插入数据。我想在WHERE 条件下插入必须从TAB1 获取的数据。如果存在 fethced 数据，则在 TAB2 中插入数据。如果不是，请在TAB2 中插入空白

这里我只讨论单列。我也在插入一些其他数据。它可以作为单个 SQL 查询发生吗？我正在使用 Oracle。

这是我的演示代码。我需要这样的东西：

INSERT INTO TAB1('value1','value2',?)

 if exists(select king from TAB2 where queen='yash' )

  ?=select king from TAB2 where queen='yash'

 if not exists 
  ?=''

TAB1 和 TAB2 具有不同类型的列。

 TAB1                           TAB2
--------                     -----------------
col1 col2 col3  col4             col1 king Queen  
-----------------            ----------------

 1    jan  King   Robin            1    Alex   yash
 2    Feb  King2  Hood             2    Jhon   Shakthi

现在我想用 where 条件从 TAB2 向 TAB1 中插入数据 像这样的

insert into  TAB1(col1,col2,col3,col4)
        values(5,'MArch',King7, select king From TAB2 where Queen='yash')

如果 select king From TAB2 其中Queen='yash' 返回'Alex'，那么如果不是必须插入空白值，则必须插入。

  Here Queen column is Unique column .. So you can expect single row data only.

TAB1 and TAB2 having different column names and different column Types

Answer 1

TAB2
-----------------
 col1 king  Queen  
----------------

  1   Alex  yash
  2   Jhon  Shakthi
  3   Fred  Maya  

---

insert into  TAB1(col1,col2,col3,col4, col5)
        select 5, -- If you are tring to use an auto incremental value, I recommend you to use a trigger and Sequence on the table
              'March',
              'King7', 
              king , 
              col1 -- Col1 is used to get an Idea which row caused the Insert
             From 
        TAB2 where Queen='yash';



 TAB1                           
--------------------------------           
col1 col2   col3   col4    col5         
--------------------------------           
 5   March  King7  Alex    1    

---

insert into  TAB1(col1,col2,col3,col4, col5)
        select 5, 
              'March',
              'King7', 
              case when Queen='yash' then  king  else '' end, 
              col1 
             From 
        TAB2 ;


--------------------------------           
col1 col2   col3   col4    col5         
--------------------------------           
 5   March  King7  Alex    1     
 5   March  King7  ''      2     
 5   March  King7  ''      3    

---

---- removing insert to Col5 column
 insert into  TAB1(col1,col2,col3,col4)
        select
            distinct
            5, 
              'March',
              'King7', 
              case when Queen='yash' then  king  else '' end
              From 
        TAB2 ;

--------------------------           
col1 col2   col3   col4           
--------------------------           
 5   March  King7  Alex    
 5   March  King7  ''  

---

 insert into  TAB1(col1,col2,col3,col4)
        select
            distinct
            5,
            case when Queen='yash' then 'March' else '' end,
            case when Queen='yash' then 'King7' else '' end, 
            case when Queen='yash' then  king   else '' end
              From 
        TAB2 ;

--------------------------           
col1 col2   col3   col4           
--------------------------           
 5   March  King7  Alex    
 5   ''     ''     ''  

Answer 2

假设“插入空白”是指不进行插入，您可能希望考虑进行 INSERT SELECT。

INSERT INTO TAB1( ... )
SELECT ... FROM TAB2
WHERE ...