DOITJT的博客

INTINT[(width)] [UNSIGNED] [ZEROFILL]4 bytes in storage width = number of digits displayed!= storage width unsigned = positive number zerofill: fill left with 0 until widthExample:CREATE TABLE test_bigint (id BIGINT UNSIGNED);BIGINTBIGIN.

Add data to tablesINSERT INTO table_name VALUES(col_1, col_2, col_3, ...); // 按顺序填入所有fields，字符串要加引号, 每个field之间要加逗号，结尾要加分号Use null when the field is auto-generated override auto value by manually providing a valuef Use ignore to disregard duplic

Select rows based on column valueSELECT * FROM table_name WHERE col_name = value; // select all rows that satisfies SELECT col_1, col_2 FROM table_name WHERE col_name = value; // only specified columns from rows that satisfiesExample matching cond

Collect requirement from stakeholders Identify entities Identify primary keys Identify relationship N:M -- create intermediate relations (to convertN:M into two 1:N relationships) 1:N -- "1" side entity PK as foreign key in N...

将其他表（可以是多张表）中的列添加过来Inner Join

(i). Temporary Update Problem(ii). Incorrect Summary Problem(iii). Lost Update Problem(iv). Unrepeatable Read Problem(v). Phantom Read Problem Temporary Update Problem:数据corrupt，没来得及重输or返回原状，另一个transaction就读了这个corrupted value.The corrupted val.

Relation= table Tuple= row Attribute= column Domain= allowed set of values for an attribute SuperKey:a set of one or more attributes, identify uniquely a tuple in the relation CandidateKey:The smallest subset among all superKeys PrimaryKey: a...

Login to MySQLmysql -h localhost -u root -p-h + 主机地址;-u + Username;-p + PasswordCreate Usersgrant all on *.* to 'username'@'hostname'; // grant 所有权限 on 所有 databaseList all Users select user from mysql.user;List all DBshow databas.