1 | This is an example of ' single, " double, and \ backslash (in the messed up records)
2 | This example is how it gets stored now  backslash ' single " double

1 | This is an example of ' single, " double, and  backslash

2 | This example is how it gets stored now backslash ' single " double

1 | This is an example of ' single, " double, and  backslash (how data should be)

DROP TABLE IF EXISTS tmpTable;
CREATE TEMPORARY TABLE IF NOT EXISTS tmpTable ( BadText VARCHAR(100));

INSERT INTO tmpTable
SELECT 'This is an example of \' single, \"double, and \\ backslash';

select BadText from tmpTable;

update tmpTable
set BadText = replace(replace(replace(BadText,'\'','''),'\"','"'),'\\','\');

select BadText as GoodText from tmpTable;

SELECT REGEX_REPLACE(your_column, '.*backslash{2,}.*', 'backslash') FROM table