Lexical Structure

A BigQuery statement comprises a series of tokens. Tokens include identifiers, quoted identifiers, literals, keywords, operators, and special characters. Tokens can be separated by whitespace (space, backspace, tab, newline) or comments.

Identifiers

Identifiers are names that are associated with columns, tables, and other database objects.

Identifiers must begin with a letter or an underscore. Subsequent characters can be letters, numbers, or underscores. Quoted identifiers are identifiers enclosed by backtick (`) characters and can contain any character, such as spaces or symbols. However, quoted identifiers cannot be empty. Reserved Keywords can only be used as identifiers if enclosed by backticks.

Syntax (defined here as a regular expression):

[A-Za-z_][A-Za-z_0-9]*

Examples:

Customers5
_dataField1
ADGROUP

Invalid examples:

5Customers
_dataField!
GROUP

5Customers begins with a number, not a letter or underscore. _dataField! contains the special character "!" which is not a letter, number, or underscore. GROUP is a reserved keyword, and therefore cannot be used as an identifier without being enclosed by backtick characters.

Both identifiers and quoted identifiers are case insensitive, with some nuances. See Case Sensitivity for further details.

Literals

A literal represents a constant value of a built-in data type. Some, but not all, data types can be expressed as literals.

String and Bytes Literals

Both string and bytes literals must be quoted, either with single (') or double (") quotation marks, or triple-quoted with groups of three single (''') or three double (""") quotation marks.

Quoted literals:

Literal Examples Description
Quoted string
  • "abc"
  • "it's"
  • 'it\'s'
  • 'Title: "Boy"'
  • '''why\?'''
Quoted strings enclosed by single (') quotes can contain unescaped double (") quotes, and vice versa.
Backslashes (\) introduce escape sequences. See Escape Sequences table below.
Quoted strings cannot contain newlines, even when preceded by a backslash (\).
Triple-quoted string
  • """abc"""
  • '''it's'''
  • '''Title:"Boy"'''
  • '''two
    lines'''
Embedded newlines and quotes are allowed without escaping - see fourth example.
Backslashes (\) introduce escape sequences. See Escape Sequences table below.
A trailing unescaped backslash (\) at the end of a line is not allowed.
Three unescaped quotes in a row which match the starting quotes will end the string.
Raw string
  • R"abc+"
  • r'''abc+'''
  • R"""abc+"""
  • r'f\(abc,(.*),def\)'
Quoted or triple-quoted literals that have the raw string literal prefix (r or R) are interpreted as raw/regex strings.
Backslash characters (\) do not act as escape characters. If a backslash followed by another character occurs inside the string literal, both characters are preserved.
A raw string cannot end with an odd number of backslashes.
Raw strings are useful for constructing regular expressions.

Prefix characters (r, R, b, B) are optional for quoted or triple-quoted strings, and indicate that the string is a raw/regex string or a byte sequence, respectively. For example, b'abc' and b'''abc''' are both interpreted as type bytes. Prefix characters are case insensitive.

Quoted literals with prefixes:

Literal Example Description
Bytes
  • B"abc"
  • B'''abc'''
  • b"""abc"""
Quoted or triple-quoted literals that have the bytes literal prefix (b or B) are interpreted as bytes.
Raw bytes
  • br'abc+'
  • RB"abc+"
  • RB'''abc'''
The r and b prefixes can be combined in any order. For example, rb'abc*' is equivalent to br'abc*'.

The table below lists all valid escape sequences for representing non-alphanumeric characters in string and byte literals. Any sequence not in this table produces an error.

Escape Sequence Description
\a Bell
\b Backspace
\f Formfeed
\n Newline
\r Carriage Return
\t Tab
\v Vertical Tab
\\ Backslash (\)
\? Question Mark (?)
\" Double Quote (")
\' Single Quote (')
\` Backtick (`)
\ooo Octal escape, with exactly three digits (in the range 0-7). Decodes to a single Unicode character (in string literals) or byte (in bytes literals).
\xhh or \Xhh Hex escape, with exactly two hex digits (0-9 or A-F or a-f). Decodes to a single Unicode character (in string literals) or byte (in bytes literals). Examples:
  • '\x41' == 'A'
  • '\x41B' is 'AB'
  • '\x4' is an error
\uhhhh Unicode escape, with lowercase 'u' and exactly four hex digits. Valid only in string literals or identifiers.
Note that the range D800-DFFF is not allowed, as these are surrogate unicode values.
\Uhhhhhhhh Unicode escape, with uppercase 'U' and exactly eight hex digits. Valid only in string literals or identifiers.
Note that the range D800-DFFF is not allowed, as these are surrogate unicode values. Also, values greater than 10FFFF are not allowed.

Integer Literals

Integer literals are either a sequence of decimal digits (0 through 9) or a hexadecimal value that is prefixed with "0x". Integers can be prefixed by "+" or "-" to represent positive and negative values, respectively.

Examples:

123
0xABC
-123

An integer literal is interpreted as an int64. If the value is outside the int64 range of values, the literal is interpreted as a uint64. If the value is outside the uint64 range, an error is provided.

Coercion (implicit casting) of integer literals to other integer types can occur if casting does not result in truncation. For example, if the integer 55 of type int32 is compared to the integer literal 77, the literal value 77 is coerced into type int32 because 77 can be represented by the int32 type.

Floating Point Literals

Syntax options:

[+-]DIGITS.[DIGITS][e[+-]DIGITS]
[DIGITS].DIGITS[e[+-]DIGITS]
DIGITSe[+-]DIGITS

DIGITS represents one or more decimal numbers (0 through 9) and e represents the exponent marker (e or E).

Examples:

123.456e-67
.1E4
58.
4e2

Numeric literals that contain either a decimal point or an exponent marker are presumed to be type double.

Implicit coercion of floating point literals to float type is possible if the value is within the valid float range.

There is no literal representation of NaN or infinity, but the following case-insensitive strings can be explicitly cast to float:

  • "NaN"
  • "inf" or "+inf"
  • "-inf"

Array Literals

Array literals are a comma-separated lists of elements enclosed in square brackets. The ARRAY keyword is optional, and an explicit element type T is also optional.

Examples:

[1, 2, 3]
['x', 'y', 'xy']
ARRAY[1, 2, 3]
ARRAY<string>['x', 'y', 'xy']
ARRAY<int32>[]

Struct Literals

Syntax:

(elem[, elem...])

where elem is an element in the struct. elem must be a literal data type, not an expression or column name.

The output type is an anonymous struct type (structs are not named types) with anonymous fields with types matching the types of the input expressions.

Example Output Type
(1, 2, 3) STRUCT<int64,int64,int64>
(1, 'abc') STRUCT<int64,string>

Date Literals

Syntax:

DATE 'YYYY-M[M]-D[D]'

Date literals contain the DATE keyword followed by a string literal that conforms to the canonical date format, enclosed in single quotation marks. Date literals support a range between the years 1 and 9999, inclusive. Dates outside of this range are invalid.

For example, the following date literal represents September 27, 2014:

DATE '2014-09-27'

String literals in canonical date format also implicitly coerce to DATE type when used where a DATE-type expression is expected. For example, in the query

SELECT * FROM foo WHERE date_col = "2014-09-27"

the string literal "2014-09-27" will be coerced to a date literal.

Time Literals

Syntax:

TIME '[H]H:[M]M:[S]S[.DDDDDD]]'

TIME literals contain the TIME keyword and a string literal that conforms to the canonical time format, enclosed in single quotation marks.

For example, the following time represents 12:30 a.m.:

TIME '12:30:00.45'

DATETIME Literals

Syntax:

DATETIME 'YYYY-[M]M-[D]D [[H]H:[M]M:[S]S[.DDDDDD]]'

DATETIME literals contain the DATETIME keyword and a string literal that conforms to the canonical DATETIME format, enclosed in single quotation marks.

For example, the following DATETIME represents 12:30 p.m. on September 27, 2014:

DATETIME '2014-09-27 12:30:00.45'

DATETIME literals support a range between the years 1 and 9999, inclusive. DATETIMEs outside of this range are invalid.

String literals with the canonical DATETIME format implicitly coerce to a DATETIME literal when used where a DATETIME expression is expected.

For example:

SELECT * FROM foo
WHERE datetime_col = "2014-09-27 12:30:00.45"

In this query, the string literal "2014-09-27 12:30:00.45" is coerced to a DATETIME literal.

Timestamp literals

Syntax:

TIMESTAMP 'YYYY-[M]M-[D]D [[H]H:[M]M:[S]S[.DDDDDD]] [timezone]'

Timestamp literals contain the TIMESTAMP keyword and a string literal that conforms to the canonical timestamp format, enclosed in single quotation marks.

Timestamp literals support a range between the years 1 and 9999, inclusive. Timestamps outside of this range are invalid.

A timestamp literal can include a numerical suffix to indicate the timezone:

TIMESTAMP '2014-09-27 12:30:00.45-08'

If this suffix is absent, the default timezone, UTC, is used.

For example, the following timestamp represents 12:30 p.m. on September 27, 2014, using the timezone, UTC:

TIMESTAMP '2014-09-27 12:30:00.45'

For more information on timezones, see Timezone.

String literals with the canonical timestamp format, including those with timezone names, implicitly coerce to a timestamp literal when used where a timestamp expression is expected. For example, in the following query, the string literal "2014-09-27 12:30:00.45 America/Los_Angeles" is coerced to a timestamp literal.

SELECT * FROM foo
WHERE timestamp_col = "2014-09-27 12:30:00.45 America/Los_Angeles"

Timezone

Since timestamp literals must be mapped to a specific point in time, a timezone is necessary to correctly interpret a literal. If a timezone is not specified as part of the literal itself, then the default timezone value, which is set by the BigQuery implementation, is used.

Timezones are represented by strings in the following canonical format, which represents the offset from Coordinated Universal Time (UTC).

Format:

(+|-)H[H][:M[M]]

Examples:

'-08:00'
'-8:15'
'+3:00'
'+07:30'
'-7'

Timezones can also be expressed using string timezone names from the tz database. For a less comprehensive but simpler reference, see the List of tz database timezones on Wikipedia. Canonical timezone names have the format <continent/[region/]city>, such as America/Los_Angeles.

Note that not all timezone names are interchangeable even if they do happen to report the same time during a given part of the year. For example, America/Los_Angeles reports the same time as UTC-7:00 during Daylight Savings Time, but reports the same time as UTC-8:00 outside of Daylight Savings Time.

Example:

TIMESTAMP '2014-09-27 12:30:00 America/Los_Angeles'
TIMESTAMP '2014-09-27 12:30:00 America/Argentina/Buenos_Aires'

Case Sensitivity

BigQuery follows these rules for case sensitivity:

Category Case Sensitive? Notes
Keywords No  
Function names No  
Table names Yes  
Column names No  
String values Yes
String comparisons Yes  
Aliases within a query No  
Regular expression matching See Notes Regular expression matching is case sensitive by default, unless the expression itself specifies that it should be case insensitive.
LIKE matching Yes  

Reserved Keywords

Keywords are a group of tokens that have special meaning in the BigQuery language, and have the following characteristics:

  • Keywords cannot be used as identifiers unless enclosed by backtick (`) characters.
  • Keywords are case insensitive.

BigQuery has the following reserved keywords.

ALL
AND
ANY
ARRAY
AS
ASC
ASSERT_ROWS_MODIFIED
AT
BETWEEN
BY
CASE
CAST
COLLATE
CONTAINS
CREATE
CROSS
CUBE
CURRENT
DEFAULT
DEFINE
DESC
DISTINCT
ELSE
END
ENUM
ESCAPE
EXCEPT
EXCLUDE
EXISTS
EXTRACT
FALSE
FETCH
FOLLOWING
FOR
FROM
FULL
GROUP
GROUPING
GROUPS
HASH
HAVING
IF
IGNORE
IN
INNER
INTERSECT
INTERVAL
INTO
IS
JOIN
LATERAL
LEFT
LIKE
LIMIT
LOOKUP
NATURAL
NEW
NOT
NULL
MERGE
NO
NULLS
OF
ON
OR
ORDER
OUTER
OVER
PARTITION
PRECEDING
PROTO
RANGE
RECURSIVE
RESPECT
RIGHT
ROLLUP
ROWS
SELECT
SET
SOME
STRUCT
TABLESAMPLE
THEN
TO
TREAT
TRUE
UNBOUNDED
UNION
UNNEST
USING
WHEN
WHERE
WINDOW
WITH
WITHIN

Terminating Semicolons

Statements can optionally use a terminating semicolon (;) in the context of a query string submitted through an Application Programming Interface (API). Some interactive tools require statements to have a terminating semicolon. In a request containing multiple statements, statements must be separated by semicolons, but the semicolon is optional for the final statement.

Comments

Comments are sequences of characters that are ignored by the parser. BigQuery supports the following types of comments.

Single line comments

Single line comments are supported by prepending # or -- before the comment.

Examples

SELECT x FROM T; # x is a field and T is a table

Comment includes all characters from the '#' character to the end of the line.

SELECT x FROM T; --x is a field and T is a table

Comment includes all characters from the '--' sequence to the end of the line. You can optionally add a space after the '--'.

Multiline comments

Multiline comments are supported by enclosing the comment using /* <comment> */.

Example:

SELECT x FROM T /* x is a field and T is a table */
WHERE x = 3;

Invalid example:

SELECT x FROM T /* comment starts here
                /* comment ends on this line */
                this line is not considered a comment */
WHERE x = 3;

Comment includes all characters, including newlines, enclosed by the first occurrence of '/*' and the first subsequent occurrence of '*/'. Nested comments are not supported. The second example contains a nested comment that renders the query invalid.

Send feedback about...

BigQuery Documentation