# String Functions

# upper

Converts the ASCII Latin symbols in a string to uppercase.

Alias

ucase

Example

SELECT upper('a')
┌─upper('a')─┐
│ A          │
└────────────┘

# lower

Converts the ASCII Latin symbols in a string to lowercase.

Alias

lcase

Example

SELECT lower('A')
┌─lower('A')─┐
│ a          │
└────────────┘

# substring(s, offset, length)

Returns a substring with length many bytes, starting at the byte at index offset. Character indexing starts from 1.

substring(s, offset, length)

Alias

  • substr
  • mid

Example

SELECT substring('www.clickhouse.com', 5, 10)
┌─substring('www.clickhouse.com', 5, 10)─┐
│clickhouse                              │
└────────────────────────────────────────┘

# trim()

Removes the specified characters from the start or end of a string. If not specified otherwise, the function removes whitespace (ASCII-character 32).

trim([[LEADING|TRAILING|BOTH] trim_character FROM] input_string)

Arguments

  • trim_character — Specified characters for trim. String.
  • input_string — String for trim. String.

Returned value

  • A string without leading and/or trailing specified characters.
  • Type: String.

Example

SELECT trim(BOTH ' ()' FROM '( Hello, world! )');
┌─replaceRegexpAll('( Hello, world! )', concat('^[', regexpQuoteMeta(' ()'), ']+|[', regexpQuoteMeta(' ()'), ']+$'), '')─┐
│ Hello, world!                                                                                                          │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

# Length

Returns the length of a string in bytes (not: in characters or Unicode code points). The function also works for arrays.

length(s)

Arguments

  • s — Specified characters for getting length. String.

Alias

OCTET_LENGTH