是否可以在建立连接后检查MySQL数据库是否存在。
我知道如何检查一个表是否存在于一个DB，但我需要检查DB是否存在。如果不是，我必须调用另一段代码来创建它并填充它。
我知道这一切听起来有点不优雅-这是一个快速和肮脏的应用程序。
当前回答
从壳像bash
if [[ ! -z "`mysql -qfsBe "SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME='db'" 2>&1`" ]];
then
echo "DATABASE ALREADY EXISTS"
else
echo "DATABASE DOES NOT EXIST"
fi
其他回答
使用bash:
if [ "`mysql -u'USER' -p'PASSWORD' -se'USE $DATABASE_NAME;' 2>&1`" == "" ]; then
echo $DATABASE_NAME exist
else
echo $DATABASE_NAME doesn't exist
fi
下面是一个bash函数，用于检查数据库是否存在:
function does_db_exist {
local db="${1}"
local output=$(mysql -s -N -e "SELECT schema_name FROM information_schema.schemata WHERE schema_name = '${db}'" information_schema)
if [[ -z "${output}" ]]; then
return 1 # does not exist
else
return 0 # exists
fi
}
另一种选择是尝试使用数据库。注意，这也检查权限:
if mysql "${db}" >/dev/null 2>&1 </dev/null
then
echo "${db} exists (and I have permission to access it)"
else
echo "${db} does not exist (or I do not have permission to access it)"
fi
SELECT IF('database_name' IN(SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA), 1, 0) AS found;
Rails代码:
ruby-1.9.2-p290 :099 > ActiveRecord::Base.connection.execute("USE INFORMATION_SCHEMA")
ruby-1.9.2-p290 :099 > ActiveRecord::Base.connection.execute("SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'entos_development'").to_a
SQL (0.2ms) SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'entos_development'
=> [["entos_development"]]
ruby-1.9.2-p290 :100 > ActiveRecord::Base.connection.execute("SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'entos_development1'").to_a
SQL (0.3ms) SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'entos_development1'
=> []
=> entos_development存在，entos_development1不存在
Golang解决方案
创建一个测试包并添加:
import "database/sql"
// testing database creation
func TestCreate(t *testing.T){
Createdb("*Testdb") // This just calls the **sql.DB obect *Testdb
db,err := sql.Open("mysql", "root:root@tcp(127.0.0.1:3306)/*Testdb")
if err != nil{
panic(err)
}
defer db.Close()
_, err = db.Exec("USE *Testdb")
if err != nil{
t.Error("Database not Created")
}
}
