1.1 oracle syntax wmsys.wm_concat():
SELECT
NAME,
wmsys.wm_concat(subject_1) subject_1
FROM
table_name
GROUP BY
NAME
1.2 oracle syntax LISTAGG() (note, this is the syntax provided by Oracle 11g and above):
LISTAGG(measure_expr [, 'delimiter']) WITHIN GROUP (order_by_clause) [OVER query_partition_clause]
parameter description
OVER uses the OVER clause to define the window for calculation.
measure_expr can be any expression. Null values in measure columns are ignored.
delimiter specifies the string used to delimit the metric values. This clause is optional and defaults to NULL.
SELECT
NAME, listagg(subject_1, ',') within GROUP (ORDER BY NAME)
FROM table_name
GROUP BY NAME
2.1 oracle syntax wmsys.wm_concat():
Through wm_concat() in oracle, the splicing of multiple columns can be realized:
select NAME, wmsys.wm_concat(age || ‘|’ || address) msg
from TK_USER_INFO
group by NAME;
Notice:
1. In the above SQL, || '|' || means that two columns are separated by |, and '|' can be replaced by any separator
1.3 mysql语法group_concat：
SELECT
NAME,
GROUP_CONCAT(distinct subject_1 order by subject_1 asc separator ‘,’) subject_1
FROM
table_name
GROUP BY
NAME
2.2 mysql 语法CONCAT()
select name, CONCAT(age ,address) msg from tk_user_info;
Notice:
1. The result of CONCAT splicing does not have a separator
2. If any concatenated column on the right is null, then return null
2.3 mysql syntax CONCAT_WS()
select name, CONCAT_WS(‘,’,age ,address) msg from tk_user_info;
Notice:
1. This function can define a separator, CONCAT_WS() stands for CONCAT With Separator
2. The syntax is CONCAT_WS(separator,str1,str2,…), the first parameter is the separator, and the others are spliced columns.
2.4 mysql syntax GROUP_CONCAT()
select name, GROUP_CONCAT(age,‘,’,address) msg from tk_user_info group by name;
Notice:
1. Its syntax is (like the above explanation of multi-line splicing, it can perform de-redundancy, sorting, separators - different splicing columns can have different separators):
GROUP_CONCAT([DISTINCT] expr [,expr …]
[ORDER BY {unsigned_integer | col_name | formula} [ASC | DESC] [,col …]]
[SEPARATOR str_val])
2. This sql is used to splice the columns after grouping a certain column, so the SQL must be followed by group by