Returns a specific sequence of characters from the text.
SUBSTR(Campaign, 1, 6)
SUBSTR(X, start index, length)
X- literal text, a field, or an expression containing at least one field.
start index- the position from the start of the string from which to begin extracting.
length- the number of characters to extract.
- The first character of a field is at index 1.
- To begin extracting from the end of the string, use a negative index. The last character of a string is at index -1, the second to the last is at -2, etc.