tencent cloud

Aggregate Functions

COS Select supports the following aggregate functions:

Function Name	Parameter Type	Return Type
AVG(expression)	INT, FLOAT, and DECIMAL	DECIMAL will be returned if the input parameter is of integer type, and FLOAT if float type. The same type as the input parameter will be returned in all other cases.
COUNT	-	INT
MAX(expression)	INT and DECIMAL	The return value type is the same as that of the input parameter
MIN(expression)	INT and DECIMAL	The return value type is the same as that of the input parameter
SUM(expression)	INT, FLOAT, DOUBLE, and DECIMAL	INT will be returned if the input parameter is of integer type, and FLOAT if float type. The same type as the input parameter will be returned in all other cases.

Condition Functions

COS Select supports the following condition functions:

COALESCE

The COALESCE function determines the input parameters in sequence and returns the first non-null parameter value. If the input parameters do not include a non-null parameter, the function will return a null value.

Syntax

COALESCE ( expression, expression, ... )

Note：

Values, arrays, or nested functions of INT, String, and Float types can be passed in for the expression parameter.

Sample

COALESCE(1)                -- 1
COALESCE(1, null)          -- 1
COALESCE(null, null, 1)    -- 1
COALESCE(missing, 1)       -- 1
COALESCE(null, 'string')   -- 'string'
COALESCE(null)             -- null
COALESCE(null, null)       -- null
COALESCE(missing)          -- null
COALESCE(missing, missing) -- null

NULLIF

The NULLIF function determines the difference between two parameters passed in. If the two parameters have the same value, NULL will be returned; otherwise, the value of the first parameter passed in will be returned.

Syntax

NULLIF ( expression1, expression2 )

Note：

Values, arrays, or nested functions of INT, String, and Float types can be passed in for the expression parameter.

Sample

NULLIF(1, 2)             -- 1
NULLIF(1, '1')           -- 1
NULLIF(1, NULL)          -- 1
NULLIF(1, 1)             -- null
NULLIF(1.0, 1)           -- null
NULLIF(missing, null)    -- null
NULLIF(missing, missing) -- null
NULLIF([1], [1])         -- null
NULLIF(NULL, 1)          -- null
NULLIF(null, null)       -- null

Conversion Functions

COS Select supports the following conversion functions:

CAST

The CAST function converts one instance to another instance. The instance can be either a value or a function that can be calculated to a certain value.

Syntax

CAST ( expression AS data_type )

Note：

• The expression parameter can be a value, an array, an operator, or an SQL function that can be calculated to a certain value.
• The data_type parameter is the data type after conversion, such as INT. For the data types currently supported by COS Select, see Data Types.

Sample

CAST('2007-04-05T14:30Z' AS TIMESTAMP)
CAST(0.456 AS FLOAT)

Date Functions

COS Select supports the following date functions:

DATE_ADD

The DATE_ADD function adds a specified time interval to a part (year, month, day, hour, minute, or second) of a specific timestamp and returns a new timestamp.

Syntax

DATE_ADD( date_part, quantity, timestamp )

Note：

• The date_part parameter specifies the part of the timestamp to be modified, which can be year, month, day, hour, minute, or second.
• The quantity parameter represents the value to be added, which must be a positive integer.
• The timestamp parameter represents the timestamp to be modified.

Sample

DATE_ADD(year, 5, `2010-01-01T`)                -- 2015-01-01
DATE_ADD(month, 1, `2010T`)                     -- 2010-02T 
DATE_ADD(month, 13, `2010T`)                    -- 2011-02T
DATE_ADD(hour, 1, `2017T`)                      -- 2017-01-01T01:00-00:00
DATE_ADD(hour, 1, `2017-01-02T03:04Z`)          -- 2017-01-02T04:04Z
DATE_ADD(minute, 1, `2017-01-02T03:04:05.006Z`) -- 2017-01-02T03:05:05.006Z
DATE_ADD(second, 1, `2017-01-02T03:04:05.006Z`) -- 2017-01-02T03:04:06.006Z

DATE_DIFF

The DATE_DIFF function compares two valid timestamps and returns the difference between them, which can be displayed in the specified unit of time. If the date_part value of timestamp1 is greater than that of timestamp2, a positive number will be returned; otherwise, a negative number will be returned.

Syntax

DATE_DIFF( date_part, timestamp1, timestamp2 )

Note：

• The date_part parameter specifies the unit of time which the two timestamps are compared in and can be year, month, day, hour, minute, or second.
• The timestamp1 parameter is the first input timestamp.
• The timestamp2 parameter is the second input timestamp.

Sample

DATE_DIFF(year, `2010-01-01T`, `2011-01-01T`)            -- 1
DATE_DIFF(year, `2010T`, `2010-05T`)                     -- 4 
DATE_DIFF(month, `2010T`, `2011T`)                       -- 12
DATE_DIFF(month, `2011T`, `2010T`)                       -- -12
DATE_DIFF(day, `2010-01-01T23:00T`, `2010-01-02T01:00T`) -- 0 

EXTRACT

The EXTRACT function extracts a value in the specified unit of time from a given timestamp.

Syntax

EXTRACT( date_part FROM timestamp )

Note：

• The parameter date_part specifies the unit of time to be extracted, which can be year, month, day, hour, minute, or second.
• The timestamp parameter represents the input timestamp.

Sample

EXTRACT(YEAR FROM `2010-01-01T`)                           -- 2010
EXTRACT(MONTH FROM `2010T`)                                -- 1 
EXTRACT(MONTH FROM `2010-10T`)                             -- 10
EXTRACT(HOUR FROM `2017-01-02T03:04:05+07:08`)             -- 3
EXTRACT(MINUTE FROM `2017-01-02T03:04:05+07:08`)           -- 4
EXTRACT(TIMEZONE_HOUR FROM `2017-01-02T03:04:05+07:08`)    -- 7
EXTRACT(TIMEZONE_MINUTE FROM `2017-01-02T03:04:05+07:08`)  -- 8

TO_STRING

The TO_STRING function converts a timestamp to a string of time in the specified format.

Syntax

TO_STRING ( timestamp time_format_pattern )

Note：

• The timestamp parameter specifies the timestamp to be converted.
• The time_format_pattern parameter specifies the time format.

Format	Description	Sample
yy	2-digit year	98
y	4-digit year	1998
yyyy	Year expressed by 4 digits. If there are less than 4 digits, 0 will be automatically added	0199
M	Month	1
MM	Month expressed by 2 digits. If there are less than 2 digits, 0 will be automatically added	01
MMM	English abbreviation of a month	Jan
MMMM	Full English name of a month	January
MMMMM	Initial of a month	J (not applicable to the to_timestamp function)
d	Day (1-31) in a month	1
dd	Day expressed by 2 digits (1-31)	01
a	Symbol for morning or afternoon (AM/PM)	AM
h	Hour in 12-hour time	1
hh	Hour expressed by 2 digits in 12-hour time	01
H	Hour in 24-hour time	1
HH	Hour expressed by 2 digits in 24-hour time	01
m	Minute (00-59)	1
mm	Minute expressed by 2 digits in 24-hour time	01
s	Second (00-59)	1
ss	Second expressed by 2 digits in 24-hour time	01
S	Decimal part of the second (accuracy: 0.1; value range: 0.0 - 0.9)	0
SS	Decimal part of the second (accuracy: 0.01; value range: 0.00 - 0.99)	6
SSS	Decimal part of the second (accuracy: 0.001; value range: 0.000 - 0.999)	60
...	...	...
SSSSSSSSS	Decimal part of the second (accuracy: 0.000000001; value range: 0.000000000 - 0.999999999)	60000000
n	Nanosecond	60000000
X	Hour-level offset. If the offset is 0, then this will be "Z"	+01 or Z
XX or XXXX	Hour- or minute-level offset. If the offset is 0, then this will be "Z"	+0100 or Z
xxx or xxxxx	Hour- or minute-level offset. If the offset is 0, then this will be "Z"	+01:00 or Z
x	Hour-level offset	1
xx or xxxx	Hour- or minute-level offset	0100
xxx or xxxxx	Hour- or minute-level offset	01:00

Sample

TO_STRING(`1998-07-20T20:18Z`,  'MMMM d, y')                    -- "July 20, 1998"
TO_STRING(`1998-07-20T20:18Z`, 'MMM d, yyyy')                   -- "Jul 20, 1998"
TO_STRING(`1998-07-20T20:18Z`, 'M-d-yy')                        -- "7-20-69"
TO_STRING(`1998-07-20T20:18Z`, 'MM-d-y')                        -- "07-20-1998"
TO_STRING(`1998-07-20T20:18Z`, 'MMMM d, y h:m a')               -- "July 20, 1998 8:18 PM"
TO_STRING(`1998-07-20T20:18Z`, 'y-MM-dd''T''H:m:ssX')           -- "1998-07-20T20:18:00Z"
TO_STRING(`1998-07-20T20:18+08:00Z`, 'y-MM-dd''T''H:m:ssX')     -- "1998-07-20T20:18:00Z"
TO_STRING(`1998-07-20T20:18+08:00`, 'y-MM-dd''T''H:m:ssXXXX')   -- "1998-07-20T20:18:00+0800"
TO_STRING(`1998-07-20T20:18+08:00`, 'y-MM-dd''T''H:m:ssXXXXX')  -- "1998-07-20T20:18:00+08:00"

TO_TIMESTAMP

The TO_TIMESTAMP function converts a string of time to a timestamp.

Syntax

TO_TIMESTAMP ( string )

Note：

The string parameter represents the input time string.

Sample

TO_TIMESTAMP('2007T')                         -- `2007T`
TO_TIMESTAMP('2007-02-23T12:14:33.079-08:00') -- `2007-02-23T12:14:33.079-08:00`

UTCNOW

The UTCNOW function returns the current timestamp in UTC.

Syntax

UTCNOW()

Sample

UTCNOW() -- 2019-01-01T14:23:12.123Z

String Functions

COS Select supports the following string functions:

CHAR_LENGTH, CHARACTER_LENGTH

Both CHAR_LENGTH and CHARACTER_LENGTH can compute the number of characters in a string, and they have the same semantics.

Syntax

CHAR_LENGTH ( string )

Note：

The string parameter specifies the string for character counting

Sample

CHAR_LENGTH('null')      -- 4
CHAR_LENGTH('tencent')   -- 7

LOWER

The LOWER function converts all uppercase letters in the specified string to lowercase letters, with all non-uppercase letters left unchanged.

Syntax

LOWER ( string )

Note：

The string parameter specifies the string for which to convert uppercase letters to lowercase letters.

Sample

LOWER('TENcent') -- 'tencent'

SUBSTRING

The SUBSTRING function returns a substring of a string. You can specify an index from which the SUBSTRING function will extract the remainder of the original string based on the length of the specified substring and return the result.

Note：

If the input string contains only 1 character, and the index is set to be greater than 1, the SUBSTRING function will automatically switch it to 1.

Syntax

SUBSTRING( string FROM start [ FOR length ] )

Note：

• The string parameter specifies the string from which to extract a substring.
• The start parameter represents an index value of the string as the starting position for extraction.
• The length parameter specifies the length of the substring. If the length of the substring is not specified, the remainder of the string will be extracted.

Sample

SUBSTRING("123456789", 0)      -- "123456789"
SUBSTRING("123456789", 1)      -- "123456789"
SUBSTRING("123456789", 2)      -- "23456789"
SUBSTRING("123456789", -4)     -- "123456789"
SUBSTRING("123456789", 0, 999) -- "123456789" 
SUBSTRING("123456789", 1, 5)   -- "12345"

TRIM

The TRIM function deletes all characters before the first character or after the last character of the specified string. " " is the default character to be deleted.

Syntax

TRIM ( [[LEADING | TRAILING | BOTH remove_chars] FROM] string )

Note：

• The string parameter specifies the string to be manipulated.
• The LEADING | TRAILING | BOTH parameter specifies the extra characters to be deleted, which can be before the string (LEADING), after the string (TRAILING), or both (BOTH).
• The remove_chars parameter specifies the type of extra characters to be deleted. It can be a string containing more than one characters. The TRIM function will delete all extra characters of the corresponding type that are identified by the TRIM function before or after the string parameter.

Sample

TRIM('       foobar         ')               -- 'foobar'
TRIM('      \tfoobar\t         ')            -- '\tfoobar\t'
TRIM(LEADING FROM '       foobar         ')  -- 'foobar'
TRIM(TRAILING FROM '       foobar         ') -- 'foobar'
TRIM(BOTH FROM '       foobar         ')     -- 'foobar'
TRIM(BOTH '12' FROM '1112211foobar22211122') -- 'foobar'

UPPER

The UPPER function converts all lowercase letters to uppercase letters with non-lowercase letters left unchanged.

Syntax

UPPER ( string )

Note：

The string parameter specifies the string to be converted to uppercase letters.

Sample

UPPER('tenCENT') -- 'TENCENT'