regexp_like to selects rows where an attribute string contains several different words - sql

Question

A bit new to regexp and looking for some help understanding some of the capabilities. I'am currently trying to select some sets of data that start with a word followed by a space and then several possible words.
Example 1:
I am basically looking to select data such as Product1 green, Product1 red, Product1 blue (green, red or blue basically) but not:
xyz Product1, Product1 black, Product1 white, Product1 garbage red.
I have tried to the following queries with not much success:
Where regexp_like(item, 'Product1 [green | red | blue]');
Where regexp_like(item, 'Product1 [green, red, blue]');
Where regexp_like(item, '^Product1 [green, red, blue]');
Hypothetically, does anybody know of a way I could also implement an 'AND', for example selecting items which contain the words green and red in the same attribute.
Example 2:
Similar situation, but trying to match a word after a punctuation
Where regexp_like (job, 'Commerce [[:punct:]] .*');
With this query I am looking to select jobs which have
Commerce - test
Commerce : abcdefg
These queries are not working as I would expect them to and I'm not able to quite figure out why. I am assuming I have misunderstood the construct of these regular expressions.
Any help / explanations would be greatly appreciated!

Answer 1

For the first, try the following
WHERE REGEXP_LIKE(ITEM, '^Product1.*(green|red|blue)')
or
WHERE REGEXP_LIKE(ITEM, '^Product1 (green|red|blue)')
or
WHERE REGEXP_LIKE(ITEM, '^Product1 +(green|red|blue)')
depending on what you expect after the Product1 - the first case allows zero or more characters of any kind, the second requires that there be a single space after Product1, and the third requires one or more blanks after Product1.
Not sure where you're going exactly on the second one. If you really want strings that begin with 'Commerce', followed by a space, followed by a punctuation character, another space, and then anything, try
WHERE REGEXP_LIKE(JOB, '^Commerce [:punct:] .*');
If instead of a punctuation character you're looking for either ':' or '-', try
WHERE REGEXP_LIKE(JOB, '^Commerce [:-] .*');
I'm no great expert on regular expressions but I'll try to offer some explanations:
^ requires that the following element be at the beginning of the string. Thus, in the first case ^Product1 means "'Product1' must be at the the start of the string".
In regular expressions parentheses are used to group expressions, so in the first case (green|red|blue) are grouped together.
| is a logical OR, so (green|red|blue) means "must be one of 'green' or 'red' or 'blue'".
Square brackets are used for character classes. You can use either predefined classes, such as :punct: or :space:, or you can make up your own as in [:-]. During regular expression interpretation a square bracket character class, no matter how long, represents a single character in the string being matched. So in the regular expression ^Commerce [:-] .* the character class [:-] means "look for either a colon or a dash". If you want to indicate that you expect multiple occurrences of characters in the class, one after another, use one of the repetition operators (* or +) after the class - so [abc]* would match all of abcabcabc.
Also keep in mind that in a regular expression every character means something, so you can't use whitespace to make regular expressions more legible because the whitespace becomes something that will be looked for when the expression is interpreted.
Share and enjoy.
Edit
Didn't notice your question about AND earlier. A simple way to AND together multiple expressions is to just put them one after another. To look for (green|red|blue), followed by a space, followed by (green|red|blue) a simple expression would be
WHERE REGEXP_LIKE(ITEM, '^Product1 (green|red|blue) (green|red|blue)')
If potentially multiple spaces were to be allowed between the colors
WHERE REGEXP_LIKE(ITEM, '^Product1 (green|red|blue) +(green|red|blue)')
could be used.
Resistance is useless.