“delete 系别表”与“drop table 系别表”两者有什么不同？

在 SQL 中，`DELETE` 和 `DROP` 都可以用来删除表，但是它们的作用不同。

- `DELETE` 用于删除表中的数据，但是不删除表本身，也不释放表占用的空间。语法如下：

  DELETE FROM 表名;

- `DROP` 用于删除整个表，包括表结构和表中的数据，同时也会释放表占用的空间。语法如下：

  DROP TABLE 表名;

因此，“delete 系别表”只会删除系别表中的数据，而表本身仍然存在，而“drop table 系别表”则会删除整个系别表，包括表结构和表中的数据，同时也会释放表占用的空间。

相关问题

给出sql server postsql 不同的保留关键字的差异

SQL Server 和 PostgreSQL 的保留关键字有一些不同。其中，SQL Server 的保留关键字包括：ADD, ALTER, AS, ASC, AUTHORIZATION, BACKUP, BEGIN, BREAK, BROWSE, BULK, BY, CASCADE, CASE, CHECK, CHECKPOINT, CLOSE, CLUSTERED, COALESCE, COLLATE, COLUMN, COMMIT, COMPUTE, CONSTRAINT, CONTAINS, CONTAINSTABLE, CONTINUE, CONVERT, CREATE, CROSS, CURRENT, CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP, CURRENT_USER, CURSOR, DATABASE, DBCC, DEALLOCATE, DECLARE, DEFAULT, DELETE, DENY, DESC, DISK, DISTINCT, DISTRIBUTED, DOUBLE, DROP, DUMP, ELSE, END, ERRLVL, ESCAPE, EXCEPT, EXEC, EXECUTE, EXISTS, EXIT, EXTERNAL, FETCH, FILE, FILLFACTOR, FOR, FOREIGN, FREETEXT, FREETEXTTABLE, FROM, FULL, FUNCTION, GOTO, GRANT, GROUP, HAVING, HOLDLOCK, IDENTITY, IDENTITY_INSERT, IDENTITYCOL, IF, IN, INDEX, INNER, INSERT, INTERSECT, INTO, IS, JOIN, KEY, KILL, LEFT, LIKE, LINENO, LOAD, MERGE, NATIONAL, NOCHECK, NONCLUSTERED, NOT, NULL, NULLIF, OF, OFF, OFFSETS, ON, OPEN, OPENDATASOURCE, OPENQUERY, OPENROWSET, OPENXML, OPTION, OR, ORDER, OUTER, OVER, PERCENT, PLAN, PRECISION, PRIMARY, PRINT, PROC, PROCEDURE, PUBLIC, RAISERROR, READ, READTEXT, RECONFIGURE, REFERENCES, REPLICATION, RESTORE, RESTRICT, RETURN, REVERT, REVOKE, RIGHT, ROLE,ROLLBACK, ROWCOUNT, ROWGUIDCOL, RULE, SAVE, SCHEMA, SELECT, SESSION_USER, SET, SETUSER, SHUTDOWN, SOME, STATISTICS, SYSTEM_USER, TABLE, TABLESAMPLE, TEXTSIZE, THEN, TO, TOP, TRAN, TRANSACTION, TRIGGER, TRUNCATE, TSEQUAL, UNION, UNIQUE, UNPIVOT, UPDATE, UPDATETEXT, USE, USER, VALUES, VARYING, VIEW, WAITFOR, WHEN, WHERE, WHILE, WITH, WITHIN GROUP, WRITETEXT。

而 PostgreSQL 的保留关键字包括：ALL, ANALYSE, ANALYZE, AND, ANY, ARRAY, AS, ASC, ASYMMETRIC, AUTHORIZATION, BINARY, BOTH, CASE, CAST, CHECK, COLLATE, COLUMN, CONSTRAINT, CREATE, CROSS, CURRENT_CATALOG, CURRENT_DATE, CURRENT_ROLE, CURRENT_SCHEMA, CURRENT_TIME, CURRENT_TIMESTAMP, CURRENT_USER, DEFAULT, DEFERRABLE, DESC, DISTINCT, DO, ELSE, END, EXCEPT, FALSE, FETCH, FOR, FOREIGN, FREEZE, FROM, FULL, GRANT, GROUP, HAVING, ILIKE, IN, INITIALLY, INNER, INTERSECT, INTO, IS, ISNULL, JOIN, LATERAL, LEADING, LEFT, LIKE, LIMIT, LOCALTIME, LOCALTIMESTAMP, NATURAL, NOT, NOTNULL, NULL, OFFSET, ON, ONLY, OR, ORDER, OUTER, OVERLAPS, PLACING, PRIMARY, REFERENCES, RETURNING, RIGHT, SELECT, SESSION_USER, SIMILAR, SOME, SYMMETRIC, TABLE, TABLESAMPLE, THEN, TO, TRAILING, TRUE, UNION, UNIQUE, USER, USING, VARIADIC, VERBOSE, WHEN, WHERE, WINDOW, WITH。

以上是两者保留关键字的差异。