ALTER TABLE products ADD COLUMN description text CHECK (description <> '');
时间: 2024-05-22 16:12:03 浏览: 13
As an AI language model, I do not have access to a specific database to execute the SQL query. However, the above SQL query can be used to add a new column named "description" of data type text to the "products" table. Additionally, a CHECK constraint is added to ensure that the "description" column cannot be empty. The constraint checks if the value of the "description" column is not equal to an empty string.
相关问题
alter table add column
在 MySQL 中,可以使用 ALTER TABLE 语句来为表添加新的列。语法如下:
ALTER TABLE table_name
ADD COLUMN column_name column_definition [FIRST|AFTER existing_column];
- table_name 是你要添加新列的表的名称。
- column_name 是新列的名称。
- column_definition 是新列的数据类型和其它约束条件,如 NOT NULL 或 UNSIGNED。
- FIRST 表示在表的第一列之前插入新列,AFTER existing_column表示在某一列之后插入新列。
示例:
```
ALTER TABLE orders
ADD COLUMN order_date DATE NOT NULL;
```
这条语句会在 orders 表中添加一个名为 order_date 的 DATE 类型的列,该列不能为空。
It's not supported to alter table add serial column
Actually, it is possible to add a serial column to an existing table in PostgreSQL using the ALTER TABLE statement. The syntax for adding a serial column is as follows:
```
ALTER TABLE table_name ADD COLUMN column_name SERIAL;
```
This will create a new column called "column_name" that will automatically generate a unique integer value for each new row that is inserted into the table. You can also specify additional options for the serial column, such as the starting value and the increment value, by using the following syntax:
```
ALTER TABLE table_name ADD COLUMN column_name SERIAL [OPTIONS];
```
For example, to set the starting value for the serial column to 100 and the increment value to 10, you can use the following command:
```
ALTER TABLE my_table ADD COLUMN serial_id SERIAL START WITH 100 INCREMENT BY 10;
```
Note that if you are using an older version of PostgreSQL (prior to version 10), you may need to use a different syntax to add a serial column to an existing table. In that case, you can use the following command:
```
ALTER TABLE table_name ADD COLUMN column_name SERIAL PRIMARY KEY;
```
This will create a new serial column and set it as the primary key for the table.
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