ddl

MySQL (一) 数据库定义语言(DDL) CREATE/DROP/ALTER 文章导航 18 June 2015 更多 MYSQL 之 数据定义语言(结构定义): Data Definition Language 第一: 创建CREATE 1 创建数据库/模式: CREATE DATABASE/SCHEME 语法 Syntax: create {database | schema} [IF NOT EXISTS] db_name [create_specification [, create_specification] ...]; create_specification 选项: [DEFAULT] CHARACTER SET charset_name | [DEFAULT] COLLATE collation_name; # 栗子: 1. create database blog; 2. create database if not exist blog; 3. create database blog; default character set utf8; 4. create database if not exists blog default character set utf8; 5. create schema blog default character

MySQL (一) 数据库定义语言(DDL) CREATE/DROP/ALTER 文章导航 18 June 2015 更多 MYSQL 之 数据定义语言(结构定义): Data Definition Language 第一: 创建CREATE 1 创建数据库/模式: CREATE DATABASE/SCHEME 语法 Syntax: create {database | schema} [IF NOT EXISTS] db_name [create_specification [, create_specification] ...]; create_specification 选项: [DEFAULT] CHARACTER SET charset_name | [DEFAULT] COLLATE collation_name; # 栗子: 1. create database blog; 2. create database if not exist blog; 3. create database blog; default character set utf8; 4. create database if not exists blog default character set utf8; 5. create schema blog default character

How do I correct the error from MySQL 'you can only have one auto increment column'. CREATE TABLE book ( id INT AUTO_INCREMENT NOT NULL, accepted_terms BIT(1) NOT NULL, accepted_privacy BIT(1) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1; My MySQL says "Incorrect table definition; there can be only one auto column and it must be defined as a key " So when I added primary key as below it started working: CREATE TABLE book ( id INT AUTO_INCREMENT NOT NULL, accepted_terms BIT(1) NOT NULL, accepted_privacy BIT(1) NOT NULL, primary key (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; The full error

I've seen many times the following syntax which defines a column in a create/alter DDL statement: ALTER TABLE tbl ADD COLUMN col VARCHAR(20) NOT NULL DEFAULT "MyDefault" The question is: since a default value is specified, is it necessary to also specify that the column should not accept NULLs ? In other words, doesn't DEFAULT render NOT NULL redundant ? DEFAULT is the value that will be inserted in the absence of an explicit value in an insert / update statement. Lets assume, your DDL did not have the NOT NULL constraint: ALTER TABLE tbl ADD COLUMN col VARCHAR(20) DEFAULT "MyDefault" Then you

I'm looking at the MySQL docs here and trying to sort out the distinction between FOREIGN KEYs and CONSTRAINTs. I thought an FK was a constraint, but the docs seem to talk about them like they're separate things. The syntax for creating an FK is (in part)... [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name, ...) REFERENCES tbl_name (index_col_name,...) So the "CONSTRAINT" clause is optional. Why would you include it or not include it? If you leave it out does MySQL create a foreign key but not a constraint? Or is it more like a "CONSTRAINT" is nothing more than a name for you FK,

extract E_LOT1 userid username, password password exttrail /cdcdata/ogg_fab/dirdat/aa TranlogOptions DBLOGREADER discardfile /cdcdata/ogg_fab/dirdat/E_LOT1_discard.txt, append, megabytes 1000 DDL & INCLUDE MAPPED OBJTYPE 'TABLE' & INCLUDE MAPPED OBJTYPE 'INDEX' & INCLUDE MAPPED OBJTYPE 'SEQUENCE' & INCLUDE MAPPED OBJTYPE 'VIEW' & INCLUDE MAPPED OBJTYPE 'PROCEDURE' & INCLUDE MAPPED OBJTYPE 'FUNCTION' & INCLUDE MAPPED OBJTYPE 'PACKAGE' & EXCLUDE OPTYPE COMMENT EXTRACT P_LOT1 PASSTHRU RMTHOST 10.95.97.22, MGRPORT 7839, compress RMTTRAIL /cdcdata/ogg_mdw/dirdat/ba discardfile /cdcdata/ogg_fab

一、DML DML（data manipulation language）数据操纵语言： 　　　　就是我们最经常用到的 SELECT、UPDATE、INSERT、DELETE。 主要用来对数据库的数据进行一些操作。 SELECT 列名称 FROM 表名称 UPDATE 表名称 SET 列名称 = 新值 WHERE 列名称 = 某值 INSERT INTO table_name (列1, 列2,...) VALUES (值1, 值2,....) DELETE FROM 表名称 WHERE 列名称 = 值 1.SELECT - retrieve data from the a database 查询 2.INSERT - insert data into a table添加 3.UPDATE - updates existing data within a table 更新 4.DELETE - deletes all records from a table, the space for the records remain 删除 5.CALL - call a PL/SQL or Java subprogram 6.EXPLAIN PLAN - explain access path to data Oracle RDBMS执行每一条SQL语句，都必须经过Oracle优化器的评估

I have the following table: CREATE TABLE child( id INTEGER PRIMARY KEY, parent_id INTEGER CONSTRAINT parent_id REFERENCES parent(id), description TEXT); How do I drop the constraint? SQLite does not (as of this answer) support the alter table drop constraint command. The allowed syntax can be seen here . You will need to create a new table without a constraint, transfer the data, then delete the old table. I think something like the following should work: CREATE TABLE child2 ( id INTEGER PRIMARY KEY, parent_id INTEGER, description TEXT ); INSERT INTO child2 (id, parent_id, description) SELECT