1、mysql默认值相关查询1.1 列出 MySQL 数据库中的表默认值select table_schema as database_name, table_name, column_name, column_defaultfrom information_schema.columnswhere column_default is not null and table_schema not in ('information_schema', 'sys', 'performance_schema','mysql')-- and table_schema = 'your database name'order by table_schema, table_name, ordinal_position;

说明：

database_name - 数据库的名称（模式）table_name - 表的名称column_name - 列的名称column_default - 定义此列默认值的 SQL 表达式

1.2 MySQL数据库默认值汇总select column_default, count(distinct concat(col.table_schema, '.', col.table_name)) as tables, count(column_name) as column**rom information_schema.columns coljoin information_schema.tables tab on col.table_schema = tab.table_schema and col.table_name = tab.table_namewhere col.table_schema not in ('sys', 'information_schema', 'mysql', 'performance_schema') and tab.table_type = 'BASE TABLE'group by column_defaultorder by tables desc, columns desc;

说明：

column_default -为没有默认值的列定义默认约束（公式）和NULLtables- 具有此约束的表数（或具有对NULL行没有约束的列的表数）columns - 具有此特定约束的列数（或NULL行没有约束）

2、约束2.1 列出了数据库（模式）中的所有不可为空的列select tab.table_schema as database_name, tab.table_name, col.ordinal_position as column_id, col.column_name, col.data_type, case when col.numeric_precision is not null then col.numeric_precision else col.character_maximum_length end as max_length, case when col.datetime_precision is not null then col.datetime_precision when col.numeric_scale is not null then col.numeric_scale else 0 end as 'precision'from information_schema.tables as tabjoin information_schema.columns as col on col.table_schema = tab.table_schema and col.table_name = tab.table_name and col.is_nullable = 'no'where tab.table_schema not in ('information_schema', 'sys', 'mysql','performance_schema') and tab.table_type = 'BASE TABLE' -- and tab.table_schema = 'database name'order by tab.table_schema, tab.table_name, col.ordinal_position;

注意：如果您需要特定数据库（模式）的信息，请取消注释 where 子句中的条件并提供您的数据库名称。

说明：

database_name - 数据库的名称（模式）table_name - 表的名称column_id - 列在表中的位置column_name - 列的名称data_type - 列数据类型max_length - 数据类型的最大长度precision- 数据类型的精度

2.2 检查 MySQL 数据库中的列是否可为空select c.table_schema as database_name, c.table_name, c.column_name, case c.is_nullable when 'NO' then 'not nullable' when 'YES' then 'is nullable' end as nullablefrom information_schema.columns cjoin information_schema.tables t on c.table_schema = t.table_schema and c.table_name = t.table_namewhere c.table_schema not in ('mysql', 'sys', 'information_schema', 'performance_schema') and t.table_type = 'BASE TABLE' -- and t.table_schema = 'database_name' -- put your database name hereorder by t.table_schema, t.table_name, c.column_name;

说明：

database_name - 数据库名称（模式）table_name - 表名column_name - 列名nullable- 列的可空性属性：is nullable- 可以为空，not nullable- 不可为空

sql默认值（DBA技术分享五mysql默认值和约束的查询方法）