问题
mysql 5.7 创建text字段的时候，报错。不支持设置默认值。
bash
[1101] [42000]: BLOB, TEXT, GEOMETRY or JSON column 'xxx' can't have a default value测试1
你能给mysq5.7 8.0 的 BLOB, TEXT, GEOMETRY, and JSON data types, 字段配置默认值 NULL
bash
mysql 5.7.44
============
mysql [localhost:5744] {msandbox} (test) > CREATE TABLE t1_default (b BLOB DEFAULT null,t TEXT DEFAULT null,j JSON DEFAULT null,p POINT DEFAULT null);
Query OK, 0 rows affected (0.01 sec)
mysql [localhost:5744] {msandbox} (test) > show create table t1_defaultG
*************************** 1. row ***************************
Table: t1_default
Create Table: CREATE TABLE `t1_default` (
`b` blob,
`t` text,
`j` json DEFAULT NULL,
`p` point DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
mysql 8.0.13
============
mysql [localhost:8013] {msandbox} (test) > CREATE TABLE t1_default (b BLOB DEFAULT null,t TEXT DEFAULT null,j JSON DEFAULT null,p POINT DEFAULT null);
Query OK, 0 rows affected (0.11 sec)
mysql [localhost:8013] {msandbox} (test) > show create table t1_defaultG
*************************** 1. row ***************************
Table: t1_default
Create Table: CREATE TABLE `t1_default` (
`b` blob,
`t` text,
`j` json DEFAULT NULL,
`p` point DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci测试2
在MySQL 8.0.13版本, 之前 BLOB, TEXT, GEOMETRY, and JSON 不能配置非null 的默认值，包括表达式。
bash
mysql 5.7.44
============
mysql [localhost:5744] {msandbox} (test) > CREATE TABLE t1_default (b BLOB DEFAULT 'Blob',t TEXT DEFAULT 'Text',j JSON DEFAULT '{"key1": "value1", "key2": "value2"}',p POINT DEFAULT 'Point(0,0)');
ERROR 1101 (42000): BLOB, TEXT, GEOMETRY or JSON column 'b' can't have a default value
mysql [localhost:5744] {msandbox} (test) > CREATE TABLE t2_default(b BLOB DEFAULT ('Blob'),t TEXT DEFAULT ('Text'),j JSON DEFAULT ('{"key1": "value1", "key2": "value2"}'),p POINT DEFAULT (Point(0,0)));
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '('Blob'),t TEXT DEFAULT ('Text'),j JSON DEFAULT ('{"key1": "value1", "key2": "va' at line 1
mysql 8.0.12
============
mysql [localhost:8012] {msandbox} (test) > CREATE TABLE t1_default (b BLOB DEFAULT 'Blob',t TEXT DEFAULT 'Text',j JSON DEFAULT '{"key1": "value1", "key2": "value2"}',p POINT DEFAULT 'Point(0,0)');
ERROR 1101 (42000): BLOB, TEXT, GEOMETRY or JSON column 'b' can't have a default value
mysql [localhost:8012] {msandbox} (test) > CREATE TABLE t2_default(b BLOB DEFAULT ('Blob'),t TEXT DEFAULT ('Text'),j JSON DEFAULT ('{"key1": "value1", "key2": "value2"}'),p POINT DEFAULT (Point(0,0)));
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '('Blob'),t TEXT DEFAULT ('Text'),j JSON DEFAULT ('{"key1": "value1", "key2": "va' at line 1测试三
在MySQL 8.0.13之后 BLOB, TEXT, GEOMETRY, and JSON data types 不能直接配置非null 默认值。
bash
mysql 8.0.13
============
mysql [localhost:8013] {msandbox} (test) > CREATE TABLE t1_default (b BLOB DEFAULT 'Blob',t TEXT DEFAULT 'Text',j JSON DEFAULT '{"key1": "value1", "key2": "value2"}',p POINT DEFAULT 'Point(0,0)');
ERROR 1101 (42000): BLOB, TEXT, GEOMETRY or JSON column 'b' can't have a default value
mysql 8.0.14
============
mysql [localhost:8014] {msandbox} (test) > CREATE TABLE t1_default (b BLOB DEFAULT 'Blob',t TEXT DEFAULT 'Text',j JSON DEFAULT '{"key1": "value1", "key2": "value2"}',p POINT DEFAULT 'Point(0,0)');
ERROR 1101 (42000): BLOB, TEXT, GEOMETRY or JSON column 'b' can't have a default value
mysql 8.0.35
============
mysql [localhost:8035] {msandbox} (test) > CREATE TABLE t1_default (b BLOB DEFAULT 'Blob',t TEXT DEFAULT 'Text',j JSON DEFAULT '{"key1": "value1", "key2": "value2"}',p POINT DEFAULT 'Point(0,0)');
ERROR 1101 (42000): BLOB, TEXT, GEOMETRY or JSON column 'b' can't have a default value测试4
在MySQL 8.0.13之后包括（ 8.0.13） BLOB, TEXT, GEOMETRY, and JSON data types 不能配置表达式的默认值。
bash
mysql 8.0.13
============
mysql [localhost:8013] {msandbox} (test) > CREATE TABLE t2_default(b BLOB DEFAULT ('Blob'),t TEXT DEFAULT ('Text'),j JSON DEFAULT ('{"key1": "value1", "key2": "value2"}'),p POINT DEFAULT (Point(0,0)));
Query OK, 0 rows affected (0.07 sec)
mysql [localhost:8013] {msandbox} (test) > show create table t2_defaultG
*************************** 1. row ***************************
Table: t2_default
Create Table: CREATE TABLE `t2_default` (
`b` blob DEFAULT (_utf8mb4'Blob'),
`t` text DEFAULT (_utf8mb4'Text'),
`j` json DEFAULT (_utf8mb4'{"key1": "value1", "key2": "value2"}'),
`p` point DEFAULT (point(0,0))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.01 sec)
mysql 8.0.14
============
mysql [localhost:8014] {msandbox} (test) > CREATE TABLE t2_default(b BLOB DEFAULT ('Blob'),t TEXT DEFAULT ('Text'),j JSON DEFAULT ('{"key1": "value1", "key2": "value2"}'),p POINT DEFAULT (Point(0,0)));
Query OK, 0 rows affected (0.03 sec)
mysql [localhost:8014] {msandbox} (test) > show create table t2_defaultG
*************************** 1. row ***************************
Table: t2_default
Create Table: CREATE TABLE `t2_default` (
`b` blob DEFAULT (_utf8mb4'Blob'),
`t` text DEFAULT (_utf8mb4'Text'),
`j` json DEFAULT (_utf8mb4'{"key1": "value1", "key2": "value2"}'),
`p` point DEFAULT (point(0,0))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.01 sec)
mysql 8.0.35
============
mysql [localhost:8035] {msandbox} (test) > CREATE TABLE t2_default(b BLOB DEFAULT ('Blob'),t TEXT DEFAULT ('Text'),j JSON DEFAULT ('{"key1": "value1", "key2": "value2"}'),p POINT DEFAULT (Point(0,0)));
Query OK, 0 rows affected (0.03 sec)
mysql [localhost:8035] {msandbox} (test) > show create table t2_defaultG
*************************** 1. row ***************************
Table: t2_default
Create Table: CREATE TABLE `t2_default` (
`b` blob DEFAULT (_utf8mb4'Blob'),
`t` text DEFAULT (_utf8mb4'Text'),
`j` json DEFAULT (_utf8mb4'{"key1": "value1", "key2": "value2"}'),
`p` point DEFAULT (point(0,0))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.02 sec)