How to add empty rows to the JQGrid?

How to add a constraint to limit the number of rows you can create?

• I can't find how to add a constraint that prevents anymore than for example 5 rows from being added to a database does anyone have the syntax for this? thanks in advance :)

• Answer:

  Depends on the database system, but a way is to have an integer column, that must be unique, and must be in a certain range. Auto-increment or sequences can help here. For example: create table example ( id integer not null check (id between 1 and 5) unique, data text not null -- Other columns here ); When you insert into the table, you need to provide a unique ID value, this can be done with inner select, auto_increment, or sequence. I'll show the inner select: insert into example (id, data) values ( coalesce((select max(id) from example)+1, 1), 'Example data' ); I can insert five times then I get an error (tested in PostgreSQL 8.3). To remove is a little trickier, since you need to adjust other ID values: If we want to remove id=3: begin; delete from example where id=3; update example set id=id-1 where id>3; commit; The update here on a unique column is very sensitive to database system. --------------------------------------… Another approach is to use a trigger (PostgreSQL 8.3 again): CREATE TABLE example ( data text not null ); CREATE FUNCTION example_trigger_after() RETURNS trigger AS $$ BEGIN IF (SELECT COUNT(*) FROM example) > 5 THEN RAISE EXCEPTION 'Too many rows'; END IF; RETURN NULL; END; $$ LANGUAGE plpgsql; CREATE CONSTRAINT TRIGGER example_trigger_after AFTER INSERT ON example FOR EACH ROW EXECUTE PROCEDURE example_trigger_after(); insert into example values('Test'); INSERT 0 1 insert into example values('Test'); INSERT 0 1 insert into example values('Test'); INSERT 0 1 insert into example values('Test'); INSERT 0 1 insert into example values('Test'); INSERT 0 1 insert into example values('Test'); ERROR: Too many rows