github.com/matrixorigin/matrixone@v1.2.0/test/distributed/cases/function/func_string_instr.test (about)

     1  select instr('aaa','a');
     2  select instr('aaa','ax');
     3  select instr('aaa','aa');
     4  select instr('aaa',1);
     5  select instr('aaa','b');
     6  select instr(null,'a');
     7  select instr(1,null);
     8  select instr(null,null);
     9  select instr(null,'a');
    10  select instr('','啊');
    11  select instr('','a');
    12  select instr('',' ');
    13  select instr('','');
    14  select instr('啊','');
    15  select instr('啊',' ');
    16  select instr('啊','啊');
    17  select instr('x啊','啊');
    18  select instr('x啊啦啦啦啦啦的','啦');
    19  select instr('x啊啦啦啦啦啦的q','的');
    20  select instr('x啊啦啦啦啦啦的q','q');
    21  create table t1(a varchar,b varchar);
    22  insert into t1 values('axa','x'),('abababa','qq'),('qwer','er');
    23  select instr(a,b) from t1;
    24  select instr(a,null) from t1;
    25  select instr(null,b) from t1;
    26  select instr('axa','x') from t1;
    27  select instr(a,'qw') from t1;
    28  select instr('qwer',b) from t1;
    29  insert into t1 values('','啊'),('','a'),('',' '),('',''),('啊',''),('啊',' '),('啊','啊'),('x啊','啊'),('x啊啦啦啦啦啦的','啦'),('x啊啦啦啦啦啦的q','的'),('x啊啦啦啦啦啦的q','q');
    30  select instr(a,b) from t1;