substring, substr
Description
Extracts characters from a string and returns a substring.
If len
is not specified, this function extracts characters from the position specified by pos
. If len
is specified, this function extracts len
characters from the position specified by pos
.
pos
can be a negative integer. In this case, this function extracts characters starting from the end of the string.
Syntax
VARCHAR substr(VARCHAR str, pos[, len])
Parameter values
str
: the string to extract characters, required. It must be a VARCHAR value.pos
: the start position, required. The first position in the string is 1.length
: the number of characters to extract, optional. It must be a positive integer.
Return value
Returns a value of the VARCHAR type.
If the number of characters (len
) to return exceeds the actual length of the matching characters, all the matching characters are returned.
If the position specified by pos
exceeds the range of the string, an empty string is returned.
Examples
MySQL > select substring("starrockscluster", 1, 9);
+-------------------------------------+
| substring('starrockscluster', 1, 9) |
+-------------------------------------+
| starrocks |
+-------------------------------------+
MySQL > select substring("starrocks", -5, 5);
+-------------------------------+
| substring('starrocks', -5, 5) |
+-------------------------------+
| rocks |
+-------------------------------+
MySQL > select substring("apple", 1, 9);
+--------------------------+
| substring('apple', 1, 9) |
+--------------------------+
| apple |
+--------------------------+
keyword
substring,string,sub