sql Query Parsing in javascript

Question

I'm trying to create a javascript function that extract columns names, tables names and where conditions from a string such as "Select col1 , col2 from table1 where x = "123a" ", I wrote the following code to extract the columns names only but the problem is when I execute it, the result is weird, its 1,2,3,4,5 ! can anyone atleast explain to me why I'm getting this weird result ?

<!DOCTYPE html>
<html>
<head></head>
<body>

<button onclick = "MyFunc()">Try</button>
<p id = "y"></p>

<script>
function MyFunc(){

var str = "select col1 , col2 from table1";
var res = str.split(" ");
var cols = [];
for (x in res)
{
if (x !== "select" && x !=="from")
cols.push(x);

}
document.getElementById("y").innerHTML=cols;
}
</script>

</body>
</html>

x in is key/index of the array/object you are looping through, To get the value you need res[x] — Rhumborl
– Rhumborl, Commented Jun 10, 2016 at 11:38
You will possibly go faster if you use the browser console to inspect variables rather than casting to string and injecting into HTML. Feel free to ask any direction you need. — Álvaro González
– Álvaro González, Commented Jun 10, 2016 at 12:06

Georgi Naumov · Accepted Answer · 2016-06-10 12:04:02Z

2

Hmmm.

You can check how this work (just paste it into browser console):

var columnNames = (/\bselect\b\s+([\S\s]+?)from/i.exec("select col1 , col2 from table1") || [,""])[1].split(/\s*,\s*/g);
console.log("This column names are: " + columnNames.join(","));

or create function:

function getColumnNames(input) {
    return (/\bselect\b\s+([\S\s]+?)from/i.exec(input) || [,""])[1].split(/\s*,\s*/g);
}

answered Jun 10, 2016 at 12:04

Georgi Naumov

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3 Comments

Maryam Over a year ago

this works just perfect but what if I want to get the tables names as well as the where conditions ?

Maryam Over a year ago

oh I guess I got it :D and it seems it works: var columnNames = (/\bselect\b\s+([\S\s]+?)from/i.exec("select col1 , col2 , col3 FROM table1 , table2 WHERE x = 1 AND y = 'BQQ';") || [,""])[1].split(/\s*,\s*/g); var tables = (/\bfrom\b\s+([\S\s]+?)where/i.exec("select col1 , col2 , col3 FROM table1 , table2 WHERE x = 1 AND y = 'BQQ';") || [,""])[1].split(/\s*,\s*/g); var conditions = (/\bwhere\b\s+([\S\s]+?);/i.exec("select col1 , col2 , col3 FROM table1 , table2 WHERE x = 1 AND y = 'BQQ';") || [,""])[1].split(/\s*,\s*/g);

Álvaro González Over a year ago

Please note that you can simply do console.log("This column names are: ", columnNames);. The console is more powerful than good old alert.

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