Postgres 9.6

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CREATE TABLE dataset1
(
     id INTEGER PRIMARY KEY,
     column4 TEXT
) ;
INSERT INTO dataset1
    (id, column4)
SELECT
    i, 'column 4 for id ' || i
FROM
    generate_series(101, 120) AS s(i);
20 rows affected

CREATE TABLE dataset2
(
    column1 TEXT
) ;
INSERT INTO dataset2
    (column1)
SELECT
    'SOMETHING ' || i
FROM 
    generate_series (1001, 1020) AS s(i) ;
20 rows affected

SELECT count(DISTINCT column4) FROM dataset1 ;


count


20


WITH original_keys AS
(
    -- This creates tuples (id, rn), 
    -- where rn increases from 1 to number or rows
    SELECT 
        id, 
        row_number() OVER  () AS rn
    FROM 
        dataset1
)
, shuffled_data AS
(
    -- This creates tuples (column1, rn)
    -- where rn moves between 1 and number of rows, but is randomly shuffled
    SELECT 
        column1,
        -- The next statement is what *shuffles* all the data
        row_number() OVER  (ORDER BY random()) AS rn
    FROM 
        dataset2
)
-- You update your dataset1
-- with the shuffled data, linking back to the original keys
UPDATE
    dataset1
SET
    column4 = shuffled_data.column1
FROM
    shuffled_data
    JOIN original_keys ON original_keys.rn = shuffled_data.rn
WHERE
    dataset1.id = original_keys.id ;
20 rows affected

SELECT count(DISTINCT column4) FROM dataset1 ;


count


20


SELECT * FROM dataset1 ;


id
column4


101
SOMETHING 1014

102
SOMETHING 1019

103
SOMETHING 1001

104
SOMETHING 1009

105
SOMETHING 1008

106
SOMETHING 1013

107
SOMETHING 1016

108
SOMETHING 1010

109
SOMETHING 1007

110
SOMETHING 1020

111
SOMETHING 1005

112
SOMETHING 1003

113
SOMETHING 1017

114
SOMETHING 1018

115
SOMETHING 1004

116
SOMETHING 1015

117
SOMETHING 1011

118
SOMETHING 1002

119
SOMETHING 1012

120
SOMETHING 1006


UPDATE
    dataset1
SET
    column4 = shuffled_data.column1
FROM
    (SELECT 
        column1,
        -- The next statement is what *shuffles* all the data
        row_number() OVER  (ORDER BY random()) AS rn
    FROM 
        dataset2
    ) AS shuffled_data
    JOIN 
    (SELECT 
        id, 
        row_number() OVER  () AS rn
    FROM 
        dataset1)
    AS original_keys ON original_keys.rn = shuffled_data.rn
WHERE
    dataset1.id = original_keys.id ;
20 rows affected

SELECT * FROM dataset1;


id
column4


101
SOMETHING 1019

102
SOMETHING 1006

103
SOMETHING 1013

104
SOMETHING 1010

105
SOMETHING 1007

106
SOMETHING 1009

107
SOMETHING 1005

108
SOMETHING 1017

109
SOMETHING 1015

110
SOMETHING 1014

111
SOMETHING 1001

112
SOMETHING 1004

113
SOMETHING 1012

114
SOMETHING 1003

115
SOMETHING 1020

116
SOMETHING 1011

117
SOMETHING 1016

118
SOMETHING 1008

119
SOMETHING 1002

120
SOMETHING 1018

id	column4
101	SOMETHING 1014
102	SOMETHING 1019
103	SOMETHING 1001
104	SOMETHING 1009
105	SOMETHING 1008
106	SOMETHING 1013
107	SOMETHING 1016
108	SOMETHING 1010
109	SOMETHING 1007
110	SOMETHING 1020
111	SOMETHING 1005
112	SOMETHING 1003
113	SOMETHING 1017
114	SOMETHING 1018
115	SOMETHING 1004
116	SOMETHING 1015
117	SOMETHING 1011
118	SOMETHING 1002
119	SOMETHING 1012
120	SOMETHING 1006