PostgreSQL如果表A不包含值，则插入到表A和表B中

Question

嗨我正在尝试在postgreSql表中执行以下操作，但遇到语法问题。

伪代码：

if (tableA.column1 does not contain value1) 
{ 
    INSERT INTO tableA (column1, column2) 
    VALUES value1, value2 
} 

// do this check even if the above already existed 
if (tableB does not contain value1 and value3 in the same row) 
{ 
    // it is ok if value1 and value3 already exist in the table, just not the same row 
    INSERT INTO tableB (column1, column2) 
    VALUES (value1, value3) 
} 

return true 

与此操作的实际语法任何帮助，将不胜感激！

Answer 1

-- first insert: 
insert into tablea (col1, col2) 
select 1,2 
from tablea 
where not exists (select * from tablea where col1 = 1); 

-- second insert (same logic to apply a conditional insert) 
insert into tableb (col1, col2) 
select 1,2 
from tableb 
where not exists (select * from tableb where col1 = 1 and col2 = 2);