sql concat() function

1.concat()

The concat() function is used to concatenate two strings to form a single string

eg: employee_tbl

id

name

work_date

daily

1

John

2007-01-24

250

2

Ram

2007-05-27

270

sql:

SELECT CONCAT(id, name, work_date) FROM employee_tbl;

Results:

CONCAT(id, name, work_date)

1John2007-01-24

2Ram2007-05-27

2.concat_ws()

How to use: concat_ws(separator,str2,str2,…)

concat_ws() stands for concat with separator, which is a special form of the concat() function.

The first parameter is the delimiter of other parameters, and the position of the delimiter should be placed between the positions where the two strings are concatenated.The separator can be a string or other parameters

Note: If the delimiter is NULL, the result is also NULL, and the function will ignore any NULL value after the delimiter parameter

eg:

select concat_ws(',','11','22','33');

Results:

concat_ws(',','11','22','33')

11, 22, 33

eg:

select concat_ws(',','11','22',NULL);

Results:

concat_ws(',','11','22',NULL)

11, 22

3.group_concat()

The complete syntax is as follows:

group_concat([DISTINCT] Field to concatenate [Order BY ASC/DESC sort field] [Separator 'separator'])

eg:

id

name

1

10

1

20

2

10

2

20

3

200

3

500

sql: group by id, print the value of the name field on one line, separated by semicolons

select id,group_concat(name separator ';') from aa group by id;

Results:

id

name

1

10;20

2

10;20

3

200;500

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