SQL Functions

Last updated: 2019-10-25 16:11:39

    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, ... )

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

    Samples

    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 )

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

    Samples

    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 )
    • 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.

    Samples

    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 )
    • 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.

    Samples

    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(day, -1, `2017-01-10T`)                -- 2017-01-09 
    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 )
    • 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.

    Samples

    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 )
    • 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.

    Samples

    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 )
    • 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

    Samples

    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 )

    The string parameter represents the input time string.

    Samples

    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()

    Samples

    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 )

    The string parameter specifies the string for character counting

    Samples

    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 )

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

    Samples

    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.

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

    Syntax

    SUBSTRING( string FROM start [ FOR length ] )
    • 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.

    Samples

    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 )
    • 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.

    Samples

    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 )

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

    Samples

    UPPER('tenCENT') -- 'TENCENT'

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