Write a SQL query to create a table with three columns: id, name, and age. Add a primary key constraint on the id column. Write a SQL query to create a table with four columns: product_id, product_name, price, and quantity. Ensure that the price column cannot have negative values...
Here, the SQL command checks if a table namedCompaniesexists, and if not, it creates a table with specified columns. Create Table Using Another Existing Table In SQL, we can create a new table by duplicating an existing table's structure. Let's look at an example. -- create a backup t...
可使用 INSERT INTO 语句向空表写入数据。 SQL 约束 约束用于限制加入表的数据的类型。 可以在创建表时规定约束(通过 CREATE TABLE 语句),或者在表创建之后也可以(通过 ALTER TABLE 语句)。 我们将主要探讨以下几种约束: NOT NULL UNIQUE PRIMARY KEY FOREIGN KEY CHECK DEFAULT SQL NOT NULL 约束 NOT NULL 约束...
使用SHOW CREATE TABLE命令 查看information_schema.TABLE_CONSTRAINTS视图 查看information_schema.CHECK_CONSTRAINTS视图 constraint_name约束名称,最多包含 64 个字符。 约束名称的开头结尾中间都允许有空格,但需要用"`"标识名称的开头和结尾。 约束名称可以包含特殊字符"$"。
] referenced_table_name [ ( ref_column ) ] | CHECK ( logical_expression ) } <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } { NONCLUSTERED ( column_name [ ASC | DESC ] [ ,... n ]) | NONCLUSTERED HASH ( column_name [ ,... n ] ) WITH ...
= column_set_name XML COLUMN_SET FOR ALL_SPARSE_COLUMNS <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] ( column_name [ ASC | DESC ] [ ,... n ] ) [ WITH FILLFACTOR = fillfactor | WITH ...
IF v_partition_keyISNOTNULLTHENv_table_ddl :=v_table_ddl||' PARTITION BY '||v_partition_key;ENDIF;ENDIF; v_table_ddl :=v_table_ddl||';'||E'\n';-- suffix create statement with all of the indexes on the tableFORv_index_recordINSELECTregexp_replace(indexdef,' "?'||schemaname|...
Constraints 约束 Drop Table Truncate Table Create Table 创建表 AI检测代码解析 CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name -- (Note: TEMPORARY available in Hive 0.14.0 and later) [(col_name data_type [COMMENT col_comment], ... [constraint_specification])] ...
CREATE TABLE 将在当前数据库创建一个新的, 初始为空的表。该表将由发出此命令的用户所有。 如果给出了模式名(比如,CREATE TABLE myschema.mytable ...), 那么表是在指定模式中创建的。否则它在当前模式中创建。临时表存在于一个特殊的模式里, 因此创建临时表的时候不能给出模式名。表名字必需和同一模式中其...
WITH ( storage_parameter [= value ] [, ... ] ) | WITHOUT OIDS ] [ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ] [ TABLESPACE tablespace_name ] CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name PARTITION OF parent_table ...