Function Simulation: REPEAT()Not having any functions doesn’t mean that you can’t simulate them. You can. Take REPEAT(), for instance. Apart from the RANDOMBLOB(), you can also generate a ZEROBLOB(). It’s a blob with lots of zeros in it. But you can’t just go and do this:
That would be too easy. The problem with the zeroblob is, that when cast to a string, it is actually a zero-terminated string. Quite usual when programming in C. But hey, the first character is a zero, so the resulting string is terminated right at the beginning. How useful is that?? But here’s a trick, QUOTE() the ZEROBLOB(). That would escape all characters in hex format. In other words:
-- Simulate REPEAT('abc', 3) replace(zeroblob(3), 0, 'abc')
Nice. Now we’ve got three extra letters around twice as many zeroes as we wanted. So we’ll simply do this
quote(zeroblob(3)) yields X'000000'
Doesn’t that start to make fun? Note, I have documented this simulation also here:
-- Simulate REPEAT('abc', 3) replace(substr(quote(zeroblob(2)), 3, 3), '0', 'abc') -- Or more generally: X = 'abc', Y = 3 replace(substr(quote(zeroblob((Y + 1) / 2)), 3, Y), '0', X)
Function Simulation: LPAD() and RPAD()REPEAT() was easy. But REPEAT() was inspired by LPAD() and RPAD(), which is similar to REPEAT(), except that a character is padded to the left or right of another string, until a given length of the resulting string is reached. ZEROBLOB() will help us again! Let’s consider RPAD():
Now if this isn’t funky! This was actually something, I didn’t come up with myself. This was an answer I was given on Stack Overflow, where great minds spend lots of spare time on weird problems like this: http://stackoverflow.com/questions/6576343/how-to-simulate-lpad-rpad-with-sqlite Of course, these simulations will be part of the next version of jOOQ, so you don’t have to worry any longer about how to do LPAD(), RPAD(), and REPEAT().
-- Simulate RPAD('abc', 7, '-') 'abc' || replace(replace(substr(quote(zeroblob(4)), 3, 4), '''', ''), '0', '-') -- Or more generally: -- RPAD() Using X = 7, Y = '-', Z = 'abc' Z || replace( replace( substr( quote(zeroblob((X + 1) / 2)), 3, (X - length(Z)) ), '''', '' ), '0', Y ) -- LPAD() Using X = 7, Y = '-', Z = 'abc' replace( replace( substr( quote(zeroblob((X + 1) / 2)), 3, (X - length(Z)) ), '''', '' ), '0', Y ) || Z