MEMBER_ID INTEGER IDENTITY NOT NULL PRIMARY KEY,
    MEMBER_NAME VARCHAR(200) NOT NULL,
    MEMBER_ACCOUNT VARCHAR(50) NOT NULL,
    MEMBER_STATUS_CODE CHAR(3) NOT NULL,
    FORMALIZED_DATETIME DATETIME,
    BIRTHDATE DATE,
    REGISTER_DATETIME DATETIME NOT NULL,
    REGISTER_USER VARCHAR(200) NOT NULL,
    UPDATE_DATETIME DATETIME NOT NULL,
    UPDATE_USER VARCHAR(200) NOT NULL,
    VERSION_NO BIGINT NOT NULL

#
# The variable '$$AccessContext$$' means allcommon.AccessContext.
#
# Example:
# map:{
#     ; commonColumnMap = map:{
#         ; REGISTER_DATETIME=TIMESTAMP ; REGISTER_USER=VARCHAR
#         ; UPDATE_DATETIME=TIMESTAMP   ; UPDATE_USER=VARCHAR
#     }
#     ; beforeInsertMap = map:{
#         ; REGISTER_DATETIME = $$AccessContext$$.getAccessLocalDateTimeOnThread()
#         ; REGISTER_USER     = $$AccessContext$$.getAccessUserOnThread()

// are not included.
// Common type names include "VARCHAR", "TEXT", "NVARCHAR", "DECIMAL", "BOOL",
// "INT", and "BIGINT".
func (ct ColumnType) DatabaseTypeName() string {
	if ct.DataTypeValue.Valid {
		return ct.DataTypeValue.String
	}
	return ct.SQLColumnType.DatabaseTypeName()
}

// ColumnType returns the database type of the column. like `varchar(16)`
func (ct ColumnType) ColumnType() (columnType string, ok bool) {

	Query       *DB    // required subquery.
}

// ColumnType column type interface
type ColumnType interface {
	Name() string
	DatabaseTypeName() string                 // varchar
	ColumnType() (columnType string, ok bool) // varchar(64)
	PrimaryKey() (isPrimaryKey bool, ok bool)
	AutoIncrement() (isAutoIncrement bool, ok bool)
	Length() (length int64, ok bool)
	DecimalSize() (precision int64, scale int64, ok bool)

# | JDBC Type     | Java Native          | CSharp Native |
# | ------------------------------------------------------
# | CHAR          | java.lang.String     | String        |
# | VARCHAR       | java.lang.String     | String        |
# | LONGVARCHAR   | java.lang.String     | String        |
# | NUMERIC       | java.math.BigDecimal | decimal?      |
# | DECIMAL       | java.math.BigDecimal | decimal?      |

	"github.com/minio/minio/internal/store"
	xnet "github.com/minio/pkg/v3/net"
)

const (
	psqlTableExists          = `SELECT 1 FROM %s;`
	psqlCreateNamespaceTable = `CREATE TABLE %s (key VARCHAR PRIMARY KEY, value JSONB);`
	psqlCreateAccessTable    = `CREATE TABLE %s (event_time TIMESTAMP WITH TIME ZONE NOT NULL, event_data JSONB);`

	xnet "github.com/minio/pkg/v3/net"
)

const (
	mysqlTableExists = `SELECT 1 FROM %s;`
	// Some MySQL has a 3072 byte limit on key sizes.
	mysqlCreateNamespaceTable = `CREATE TABLE %s (
             key_name VARCHAR(3072) NOT NULL,
             key_hash CHAR(64) GENERATED ALWAYS AS (SHA2(key_name, 256)) STORED NOT NULL PRIMARY KEY,
             value JSON)
           CHARACTER SET = utf8mb4 COLLATE = utf8mb4_bin ROW_FORMAT = Dynamic;`

	if err != nil {
		t.Errorf("AutoMigrate err:%v", err)
	}

	ct, err := findColumnType(&DiffType{}, "name")
	if err != nil {
		t.Errorf("findColumnType err:%v", err)
	}

	AssertEqual(t, "varchar", strings.ToLower(ct.DatabaseTypeName()))

	err = DB.Table("diff_types").AutoMigrate(&DiffType1{})
	if err != nil {
		t.Errorf("AutoMigrate err:%v", err)
	}

    O SQLModel saberá que algo declarado como `str` será uma coluna SQL do tipo `TEXT` (ou `VARCHAR`, dependendo do banco de dados).

### Criar um Engine { #create-an-engine }
Um `engine` SQLModel (por baixo dos panos, ele é na verdade um `engine` do SQLAlchemy) é o que **mantém as conexões** com o banco de dados.

    SQLModel будет знать, что объявленное как `str` станет SQL-столбцом типа `TEXT` (или `VARCHAR`, в зависимости от базы данных).

### Создание Engine { #create-an-engine }

Объект `engine` в SQLModel (под капотом это `engine` из SQLAlchemy) **удерживает соединения** с базой данных.