Обсуждение: ERROR: missing FROM-clause entry for table "new"
I'm trying to define a trigger function that looks for changes in table A (table the trigger for the function is on) and write a delta record into table B. So if a record has a value of 100 in table A, and it is updated to 50, the function should write –50 in table B. I can get the trigger to work with static SQL statements but for the actual code, I need to use dynamic SQL because I need to alter the insert statement to B depending on what column in table A is altered. I can get the correct SQL generated but when I execute the string inside the trigger function I get an error because it doesn't seem to be able to see the NEW table when it's run with EXECUTE.
So, this works in the trigger function:
Insert into A (col1,col2,…colN)
Select new.col1,new.co2…new.colN)
This doesn't:
sql := 'Insert into A (col1,col2,…colN) ';
sql := sql || 'Select new.col1,new.co2…new.colN)';
Execute sql;
ERROR: missing FROM-clause entry for table "new"
There is nothing wrong with the resulting code from sql because if I output the string and put it in as static SQL in my trigger it works.
How do I build the string within the trigger and execute it with a reference to NEW?
Thanks in advance for the help,
James
I'm trying to define a trigger function that looks for changes in table A (table the trigger for the function is on) and write a delta record into table B. So if a record has a value of 100 in table A, and it is updated to 50, the function should write –50 in table B. I can get the trigger to work with static SQL statements but for the actual code, I need to use dynamic SQL because I need to alter the insert statement to B depending on what column in table A is altered. I can get the correct SQL generated but when I execute the string inside the trigger function I get an error because it doesn't seem to be able to see the NEW table when it's run with EXECUTE.So, this works in the trigger function:Insert into A (col1,col2,…colN)Select new.col1,new.co2…new.colN)This doesn't:sql := 'Insert into A (col1,col2,…colN) ';sql := sql || 'Select new.col1,new.co2…new.colN)';Execute sql;ERROR: missing FROM-clause entry for table "new"
There is nothing wrong with the resulting code from sql because if I output the string and put it in as static SQL in my trigger it works.
How do I build the string within the trigger and execute it with a reference to NEW?
Thanks in advance for the help,James
But especially 39.5.4
You want to make use of format and/or USING to pass in the values to a parameterized dynamic statement.
Note I linked to 9.2 but any recent version should have the behavior, if different section numbers.
In short the whole "NEW.name" is a variable and you need to build the statement the same way you would with any user-defined variable.
David J.
I'm trying to define a trigger function that looks for changes in table A (table the trigger for the function is on) and write a delta record into table B. So if a record has a value of 100 in table A, and it is updated to 50, the function should write –50 in table B. I can get the trigger to work with static SQL statements but for the actual code, I need to use dynamic SQL because I need to alter the insert statement to B depending on what column in table A is altered. I can get the correct SQL generated but when I execute the string inside the trigger function I get an error because it doesn't seem to be able to see the NEW table when it's run with EXECUTE.So, this works in the trigger function:Insert into A (col1,col2,…colN)Select new.col1,new.co2…new.colN)This doesn't:sql := 'Insert into A (col1,col2,…colN) ';sql := sql || 'Select new.col1,new.co2…new.colN)';Execute sql;ERROR: missing FROM-clause entry for table "new"
There is nothing wrong with the resulting code from sql because if I output the string and put it in as static SQL in my trigger it works.
How do I build the string within the trigger and execute it with a reference to NEW?
Thanks in advance for the help,James
But especially 39.5.4
You want to make use of format and/or USING to pass in the values to a parameterized dynamic statement.
Note I linked to 9.2 but any recent version should have the behavior, if different section numbers.
In short the whole "NEW.name" is a variable and you need to build the statement the same way you would with any user-defined variable.
David J.
---------------------------------
Thanks for the reference David. I'm now able to get the sql statement to run as dynamic sql with the following syntax
sql := 'Insert into A (col1,col2,…colN) ';sql := sql || 'values($1,$2,…$N )';Execute sql USING new.col1,new.col2…new.colN
But that still leaves me with the problem that new.col1 – colN aren't known till runtime. My list of columns could vary from 5 to 50 depending on the specific update scenario. Inside the sql string I can dynamically build $1 - $N using a counter in my loop that gets the appropriate column list but how do I dynamically build the USING list? I tried put in a text variable that contained a delimited list of columns as such:
list = new.col1,new.col2…new.colN
sql := 'Insert into A (col1,col2,…colN) ';sql := sql || 'values($1,$2,…$N )';Execute sql USING listBut that gives the error:ERROR: there is no parameter $2
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