# Using the Split String transform to break up a string column
<a name="transforms-split-string"></a>

 The Split String transform allows you to break up a string into an array of tokens using a regular expression to define how the split is done. You can then keep the column as an array type or apply an **Array To Columns** transform after this one, to extract the array values onto top level fields, assuming that each token has a meaning we know beforehand. Also, if the order of the tokens is irrelevant (for instance, a set of categories), you can use the **Explode** transform to generate a separate row for each value. 

 For example, you can split a the column “categories” using a comma as a pattern to add a column “categories\$1arr”. 


| product\$1id | categories | categories\$1arr | 
| --- | --- | --- | 
| 1 | sports,winter | [sports, winter] | 
| 2 | garden,tools | [garden, tools] | 
| 3 | videogames | [videogames] | 
| 4 | game,boardgame,social | [game, boardgame, social] | 

**To add a Split String transform:**

1. Open the Resource panel and then choose Split String to add a new transform to your job diagram. The node selected at the time of adding the node will be its parent.

1. (Optional) On the Node properties tab, you can enter a name for the node in the job diagram. If a node parent is not already selected, then choose a node from the Node parents list to use as the input source for the transform.

1. On the **Transform** tab, choose the column to split and enter the pattern to use to split the string. In most cases you can just enter the character(s) unless it has a special meaning as a regular expression and needs to be escaped. The characters that need escaping are: `\.[]{}()<>*+-=!?^$|` by adding a backslash in front of the character. For instance if you want to separate by a dot ('.') you need to enter `\.`. However, a comma doesn’t have a special meaning and can just be specified as is: `,`.  
![\[The screenshot shows the Transform tab for the Split String transform.\]](http://docs.aws.amazon.com/glue/latest/dg/images/transforms-split-string-transform-tab.png)

1. (Optional) If you want to keep the original string column, then you can enter a name for a new array column, this way keeping both the original string column and the new tokenized array column.