Original link: about oracle using find_in_set function | Elvin
1. Overview of find_in_set function
find_in_set英文逗号The function can retrieve the value (string) separated by a certain item in the data table .
find_in_set(str, strlist), str: the string to be queried; strlist: 英文逗号the string separated by
Different from MySQL?
Mysql comes with the find_in_set function, which can be used directly; oracle does not have this function, so we need to manually create the find_in_set function
2. How to query data with find_in_set function
As shown in the figure, there is a column named version_type in the table, and its values are composed of (version_type:1,2,3) strings separated by English commas.
// 在mysql中，我们可以使用find_in_set函数进行精准搜索,如下
select * from test where find_in_set('1',version_type);
// 这条语句可以查询出[列version_type]包含1的数据行
Why not use in or like?
The reason for not using in: because when using in, the column value of version_type must be equal to 1 to query the data;
The reason for not using like: If you use like, its matching method is more extensive. In the search, as long as this character is included, it will be returned. We need to get the value of 1 accurately. Like will put 1 in 11, 21, 111, etc. The values all match, so it cannot be like
find_in_set function
It can only search for specific values separated by commas, which is more precise than like, and must be in the form of 1 or 2 or 3, so the find_in_set function is more suitable when you need to get a value containing 1.
3. Create the find_in_set function in oracle
CREATE OR REPLACE FUNCTION FIND_IN_SET(piv_str1 varchar2, piv_str2 varchar2, p_sep varchar2 := ',')The default is separated by commas, and can also be replaced by other characters. like:
p_sep varchar2 := '|'
⚠️: 如果是换成其它字符隔开，则查询时需要传入隔开的字符，详细请看How to use oracle
The sql to create the function is as follows:
CREATE OR REPLACE FUNCTION FIND_IN_SET(piv_str1 varchar2, piv_str2 varchar2, p_sep varchar2 := ',')
RETURN NUMBER IS
l_idx number:=0; -- 用于计算piv_str2中分隔符的位置
str varchar2(500); -- 根据分隔符截取的子字符串
piv_str varchar2(500) := piv_str2; -- 将piv_str2赋值给piv_str
res number:=0; -- 返回结果
loopIndex number:=0;
BEGIN
-- 如果piv_str中没有分割符，直接判断piv_str1和piv_str是否相等，相等 res=1
IF instr(piv_str, p_sep, 1) = 0 THEN
IF piv_str = piv_str1 THEN
res:= 1;
END IF;
ELSE
-- 循环按分隔符截取piv_str
LOOP
l_idx := instr(piv_str,p_sep);
loopIndex:=loopIndex+1;
-- 当piv_str中还有分隔符时
IF l_idx > 0 THEN
-- 截取第一个分隔符前的字段str
str:= substr(piv_str,1,l_idx-1);
-- 判断 str 和piv_str1 是否相等，相等 res=1 并结束循环判断
IF str = piv_str1 THEN
res:= loopIndex;
EXIT;
END IF;
piv_str := substr(piv_str,l_idx+length(p_sep));
ELSE
-- 当截取后的piv_str 中不存在分割符时，判断piv_str和piv_str1是否相等，相等 res=1
IF piv_str = piv_str1 THEN
res:= loopIndex;
END IF;
-- 无论最后是否相等，都跳出循环
EXIT;
END IF;
END LOOP;
-- 结束循环
END IF;
-- 返回res
RETURN res;
END FIND_IN_SET;
4. How to use
The data is shown as follows:
1. In MySQL
The method of use is as follows:
select * from test where find_in_set('2',version_type);
// 查询列VERSION_TYPE包含2的数据行
// 查询结果为2行
2. In oracle
The method of use is as follows:
select find_in_set('1','1,2,3,4') from test
select * from test where find_in_set('1',version_type) > 0
// 查询列VERSION_TYPE包含1的数据行
// 查询结果为3行
If the function uses other delimiters, the delimiter must be passed in as follows:
select * from test where find_in_set('1',version_type,'|') > 0
// 查询列VERSION_TYPE包含1的数据行(数据由”｜“分隔)
// 查询结果为3行
5. Links for reference
Use of find_in_set() function in mysql
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