Visual FoxPro uses the default value if you use the SQL ALTER TABLEcommand to remove autoincrementing for the field. PRIMARY KEY | UNIQUE PRIMARY KEY creates a primary index for the field specified in FieldName1
Visual FoxPro uses the default value if you use the ALTER TABLE - SQL command to remove autoincrementing for the field. PRIMARY KEY | UNIQUE PRIMARY KEY creates a primary index for the field specified in FieldName1. UNIQUE creates a candidate index for the field specified in FieldName1. ...
Creates a foreign (non-primary) index, specifies the index key expression, and establishes a relationship to a parent table. You can create multiple foreign indexes for the table, but foreign index expressions must specify different fields in the table. ...
UNIQUE Creates a candidate index for the field. The candidate index tag has the same name as the field.Note Candidate indexes (created by including the UNIQUE option in CREATE TABLE or ALTER TABLE - SQL) are not the same as indexes created with the UNIQUE option in the INDEX command. An...
MySQL数据库工具类之——DataTable批量加入MySQL数据库(Net版) MySqlConnection con = new MySqlConnection(connectionString)) { con.Open(); using (MySqlCommand...cmd = new MySqlCommand(sql, con)) { foreach (MySqlParameter parameter in...cmd = new MySqlCommand(sql, con)) { foreach (MySqlParamete...
System_table_access::open_table,打开Gtid_table; Rpl_info_table_access::before_open, call lex_start and mysql_reset_thd_for_next_command open_n_lock_single_table,打开并且锁定该文件 open_and_lock_tables,常识打开文件,并且锁定文件,如果失败,则需要将已经开始的事务回滚,关闭打开的表(包括临时表),释...
OracleConnection con = new OracleConnection(constr); con.Open(); OracleCommand cmd = new OracleCommand("select count(*) from emp", con); object count = cmd.ExecuteScalar(); Console.WriteLine("There are {0} rows in table emp", count); // Clean up cmd.Dispose(); con.Dispose(); } ...
1.使用pl/sql代码实现,但要求你组合后的长度不能超出oracle varchar2长度的限制 create or replace type strings_table is table of varchar2(20); / create or replace function merge (pv in strings_table) return varchar2 is ls varchar2(4000); begin for i in 1..pv.count loop ls := ls || ...
That’s where a different verb DESCRIBE comes handy; it shows the attributes of an object, similar to what the describe command in SQL*Plus command does for a table to display the columns. Here is how you display the attributes of the physicaldisk object. Remember, unlike SQL*Plus, the ...
select ... lock in share mode; //共享锁 select ... for update; //独占锁 1. 2. 实验准备: 创建表: create table user( id INT AUTO_INCREMENT, name VARCHAR(23) NOT NULL, age INT, primary key(id) )engine = INNODB default CHARSET = utf8; ...