set @sql_mode_saved = @@session.sql_mode;
show variables like 'sql_mode';
Variable_name	Value
sql_mode	NO_ENGINE_SUBSTITUTION
set sql_mode = '';
create table t1(id int, c1 text)engine=xengine charset=utf8mb4, collate=utf8mb4_0900_ai_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
create table t1(id int, c1 text)engine=xengine charset=utf8mb4, collate=utf8mb4_general_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
create table t1(id int, c1 text)engine=xengine charset=utf8, collate=utf8_general_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
create table t1(id int, c1 text)engine=xengine charset=gbk, collate=gbk_chinese_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
create table t1(id int, c1 blob)engine=xengine charset=utf8mb4, collate=utf8mb4_0900_ai_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
create table t1(id int, c1 blob)engine=xengine charset=utf8mb4, collate=utf8mb4_general_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
create table t1(id int, c1 blob)engine=xengine charset=utf8, collate=utf8_general_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
create table t1(id int, c1 blob)engine=xengine charset=gbk, collate=gbk_chinese_ci;
insert into t1 values(1, '1111'),(2, NULL);
alter table t1 add primary key(c1(4));
alter table t1 add index(id);
select * from t1;
id	c1
2	
1	1111
delete from t1 where id=2;
select * from t1;
id	c1
1	1111
drop table t1;
set sql_mode = @sql_mode_saved;