Javascript Regex to get table name from join sql query

Question

I have a query :

select a.id, a.nama, b.alamat from tsql as a join tswl as b on a.id = b.id join tscl as c on a.id=c.id

And using regex I wanted to get the table name from the query string. 得到表名。

I tried using the regular expression :

select.*from\s+(\w+).*join\s(\w+).*

Which managed to get the first table name after "from", but skipped the second table name, and get the third table name.
Current group : [Group 1 : "tsql", Group 2 : "tscl"]

Targeted group : [Group 1 : "tsql", Group 2 : "tswl", Group 3 : "tscl"] ... and so on until the last name of the chain join query

Any help will be apreciated!

Answer 1

Your current expression does not consider the possible repetition of the from/join keywords.

You could try this expression :

(?<=from|join)\s+(\w+)

Please try it yourself here : https://regex101.com/r/qQ1rvs/1

The positive lookbehind used here (?<=...) allows to capture any words (\\w+) which are after it. In this case, every table names after these keywords are captured by this expression.

Answer 2

You could try this:

var query = 'select a.id, a.nama, b.alamat from tsql as a join tswl as b on a.id = b.id join tscl as c on a.id=c.id';
console.log(query.match(/(from|join)\s+(\w+)/g).map(e => e.split(' ')[1]))

Output:

Array(3) [ "tsql", "tswl", "tscl" ]

Answer 3

Note: The regexps discussed here will not work on most versions of MySQL because of the lame regexp parser.

Issues:

• White space
• from or join being used in a comment or string or column name, etc. (I won't tackle this.)
• Possible backtics around table name. -- handled, but with a bug
• Punctuation inside backtica -- not handled
• Possible setting that allows quotes around table name (not handled)
• Subqueries/ UNION -- The table names will be lumped together without regard for such.
• Punctuation against from/join -- FROM a JOIN(b JOIN c) -- partially(?) Handled
• Derived table FROM ( SELECT ... ) -- not handled
• Case ( from vs FROM ) -- outside the scipe of this regexp
• LEFT OUTER JOIN -- not a problem

So, this will mostly handle one table name:

\b(FROM|JOIN)\s+\`?(\w+)\`?

If JS has a way to iterate through a string, continuing where it left off, then you can get them all.

To better handle backtics and punctuation within:

\b(FROM|JOIN)\s+(\w+|`[^`]+`)

but you will need to strip the backtics when they occur.